Regression in pymdownx.snippets reintroduces sibling-prefix path traversal bypass despite restrict_base_path

Exploitation

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

CVSS

4.3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N

EPSS

• CVE-2026-46338: 0.40% estimated exploitation activity in the next 30 days; percentile 34.04 (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 pymdownx.snippets has a regression of the CVE-2023-32309 / GHSA-jh85-wwv9-24hv fix. With restrictbasepath: True (the default), the current filename.startswith(base) containment check does not enforce a directory boundary. As a result, a markdown snippet directive can read files from sibling paths that share the same prefix as basepath, such as docs vs docsinternal. The regression was introduced in PR #2039 / commit 7c13bda5b7793b172efd1abb6712e156a83fe07d, which replaced the original directory-identity check with a plain string-prefix comparison. Details The regression was introduced in commit 7c13bda5b7793b172efd1abb6712e156a83fe07d (2023-05-15, #2039 "Fix regression of snippets nested deeply under specified base path"), which relaxed the original os.path.samefile(base, os.path.dirname(filename)) check to a plain startswith(base). SnippetPreprocessor.getsnippetpath() in pymdownx/snippets.py: base is os.path.abspath(b) and has no trailing separator. str.startswith(base) is…

Published by the source

19 May 2026, 20:00 UTC

Last modified by the source

10 Sep 2026, 03:50 UTC

Source last checked

26 Oct 2026, 13:41 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-62q4-447f-wv8h

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-62q4-447f-wv8h

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# Patch Next advisory brief: CVE-2026-46338

Advisory: Regression in pymdownx.snippets reintroduces sibling-prefix path traversal bypass despite restrict_base_path
IDs: CVE-2026-46338, GHSA-62q4-447f-wv8h
Record: https://patchnext.com/advisories/cve-2026-46338 (revision 2, source checked 26 Oct 2026, 13:41 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: pymdown-extensions 10.21.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI pymdown-extensions: affected >= 10.0.1, <= 10.21.2; fixed in 10.21.3

## Suggested inspection (read-only)
- `python -m pip show pymdown-extensions`: 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 pymdown-extensions.
- 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-62q4-447f-wv8h (OSV record GHSA-62q4-447f-wv8h lists affected ranges: PyPI pymdown-extensions >=10.0.1 <10.21.3 (fixed))
- Verified: https://github.com/advisories/GHSA-62q4-447f-wv8h (GitHub-reviewed advisory GHSA-62q4-447f-wv8h lists affected ranges: PyPI pymdown-extensions >=10.0.1 <=10.21.2)

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