# urllib3's Proxy-Authorization request header isn't stripped during cross-origin redirects

Advisory record · `GHSA-34jh-p97f-mpxf`

- **Identifiers:** `GHSA-34jh-p97f-mpxf` · `CVE-2024-37891` · `PYSEC-2026-1995`
- **State:** Confirmed
- **Severity:** CVSS 4.4 Medium
- **Critical:** No
- **Weakness (CWE):** [CWE-669](https://cwe.mitre.org/data/definitions/669.html)
- **Tags:** [CWE-669](https://agentprime.io/advisories/tag/cwe-669.md)
- **Published:** 17 Jun 2024
- **Updated:** 10 Sept 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 17 Jun 2024, 21:37 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `urllib3` (PyPI): affected `<1.26.19 || >=2.0.0, <2.2.2`; fixed in `1.26.19`, `2.2.2`

## Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

> The urllib3 package, versions before 1.26.19 and from 2.0.0 before 2.2.2, does not strip the Proxy-Authorization header on cross-origin redirects when the header is set outside urllib3's proxy support. An attacker able to cause a redirect to a malicious origin could receive that header value, though the source describes this scenario as highly unlikely. Upgrade to urllib3 1.26.19 or 2.2.2, or disable redirects with redirects=False, or avoid setting Proxy-Authorization outside ProxyManager.

Written 5 Nov 2026.

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 4.4 Medium, CVSS 3.1: `CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:N/A:N`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.011, the 66th percentile, on 6 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 14:35 UTC: First seen by agentprime
- 31 Oct 2026, 14:35 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-34jh-p97f-mpxf)

## Sources

- [GitHub Advisory Database: GHSA-34jh-p97f-mpxf](https://github.com/advisories/GHSA-34jh-p97f-mpxf)
- [OSV: GHSA-34jh-p97f-mpxf](https://osv.dev/vulnerability/GHSA-34jh-p97f-mpxf)
- <https://github.com/urllib3/urllib3/security/advisories/GHSA-34jh-p97f-mpxf>
- <https://nvd.nist.gov/vuln/detail/CVE-2024-37891>
- <https://github.com/urllib3/urllib3/commit/40b6d1605814dd1db0a46e202d6e56f2e4c9a468>
- <https://github.com/urllib3/urllib3/commit/accff72ecc2f6cf5a76d9570198a93ac7c90270e>
- <https://github.com/urllib3/urllib3>
- <https://lists.debian.org/debian-lts-announce/2024/12/msg00020.html>
- <https://security.netapp.com/advisory/ntap-20240822-0003>
- <https://www.vicarius.io/vsociety/posts/proxy-authorization-header-handling-vulnerability-in-urllib3-cve-2024-37891>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-34jh-p97f-mpxf>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-34jh-p97f-mpxf/>. Everything for agents: <https://agentprime.io/llms.txt>.