GHSA-h7ww-273w-6cm8: Path Traversal

Q: Who is exposed to this issue?

Applications using pip/mistune are exposed only if they explicitly enable the Include plugin through the plugins parameter. The affected behavior is in the Include directive's path resolution and HTML rendering paths.

Q: What must an attacker be able to do to exploit it?

An attacker needs to supply or influence content processed by the enabled Include directive. ../ sequences can cause files outside the source directory to be read, and unescaped error messages or included content can introduce XSS.

Q: Is a default Mistune configuration affected?

No. The Include plugin must be explicitly enabled; the issue does not apply when that plugin is not enabled.

Q: What can be done if patching is not immediately possible?

Disable the Include plugin where possible, or prevent untrusted users from controlling Include directive content and referenced paths. Treat rendered included content and Include-related errors as untrusted because escape=True does not prevent the described XSS behavior.

Published Oct 23, 2026

Updated

The Include directive in src/mistune/directives/include.py does not validate that the resolved file path stays within the source directory, allowing path traversal via ../ sequences to read arbitrary files.

Additionally, error messages and included file contents are rendered without HTML escaping, leading to XSS even when escape=True.

Affected functions: - Path resolution (lines 27-31) - blockerror() in html.py (line 140) - renderhtmlinclude() (line 72)

The Include plugin must be explicitly enabled via the plugins parameter.

Affected Software

1 affected componentFixes available

pip/mistune<=3.2.0

3.3.0

Remediation

Recommended actions to resolve this vulnerability, in priority order.

Upgrade
Upgrade pip/mistune to a version that resolves this vulnerability.
Fixed in 3.3.0
Configuration
Only enable the Include plugin explicitly via the plugins parameter when it is required.
Mistune Include plugin plugins = explicitly enabled
Configuration
HTML-escape error messages and included file contents, including when escape=True, before rendering them.
Mistune HTML rendering HTML escaping = enabled
Compensating control
Validate that the resolved Include file path remains within the source directory before reading it, rejecting ../ path traversal sequences.

Event History

Oct 23, 2026

Advisory Published

via GitHub·08:46 PM

Data Sourced

via GitHub·08:46 PM

DescriptionWeaknessAffected Software

Frequently Asked Questions

Who is exposed to this issue?

Applications using pip/mistune are exposed only if they explicitly enable the Include plugin through the plugins parameter. The affected behavior is in the Include directive's path resolution and HTML rendering paths.

What must an attacker be able to do to exploit it?

An attacker needs to supply or influence content processed by the enabled Include directive. ../ sequences can cause files outside the source directory to be read, and unescaped error messages or included content can introduce XSS.

Is a default Mistune configuration affected?

No. The Include plugin must be explicitly enabled; the issue does not apply when that plugin is not enabled.

What can be done if patching is not immediately possible?

Disable the Include plugin where possible, or prevent untrusted users from controlling Include directive content and referenced paths. Treat rendered included content and Include-related errors as untrusted because escape=True does not prevent the described XSS behavior.

GHSA-h7ww-273w-6cm8: Path Traversal

Affected Software

Remediation

Event History

Frequently Asked Questions

Who is exposed to this issue?

What must an attacker be able to do to exploit it?

Is a default Mistune configuration affected?

What can be done if patching is not immediately possible?

Company

Resources

Contact

Frequently Asked Questions

Who is exposed to this issue?

What must an attacker be able to do to exploit it?

Is a default Mistune configuration affected?

What can be done if patching is not immediately possible?