Mistune: Arbitrary File Read via Include directive path traversal

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.9 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

EPSS

• CVE-2026-59924: 0.46% estimated exploitation activity in the next 30 days; percentile 40.11 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary A path traversal issue exists in mistune's Include directive when markdown files are processed using md.read(). A crafted include path can cause files outside the intended markdown directory to be accessed. Details The issue occurs in the Include.parse() method where user-supplied paths are joined and normalized without verifying that the resulting path remains within an expected directory. Because the final path is not restricted to a trusted base directory, path traversal sequences such as ../ may reference files outside the intended location. Proof of Concept Create a markdown file: Process it using: Impact Applications that process untrusted markdown files with the Include directive enabled may allow unintended file access. The impact depends on how the feature is used and what files are accessible to the running process. Recommended Fix Validate the resolved path and ensure it remains within an allowed directory before opening the file.

Published by the source

20 Jul 2026, 21:34 UTC

Last modified by the source

20 Jul 2026, 21:46 UTC

Source last checked

26 Oct 2026, 13:49 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-r4rv-85jg-w4mf

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-r4rv-85jg-w4mf

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# Patch Next advisory brief: CVE-2026-59924

Advisory: Mistune: Arbitrary File Read via Include directive path traversal
IDs: CVE-2026-59924, GHSA-r4rv-85jg-w4mf
Record: https://patchnext.com/advisories/cve-2026-59924 (revision 2, source checked 26 Oct 2026, 13:49 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: mistune 3.3.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI mistune: affected < 3.3.0; fixed in 3.3.0

## Suggested inspection (read-only)
- `python -m pip show mistune`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on mistune.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-r4rv-85jg-w4mf (OSV record GHSA-r4rv-85jg-w4mf lists affected ranges: PyPI mistune >=0 <3.3.0 (fixed))
- Verified: https://github.com/advisories/GHSA-r4rv-85jg-w4mf (GitHub-reviewed advisory GHSA-r4rv-85jg-w4mf lists affected ranges: PyPI mistune >=0 <3.3.0)

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