# CVE-2026-44431: urllib3 sensitive header leak in ProxyManager low-level redirects

Source: https://junglewise.ai/threats/cve-2026-44431-urllib3-sensitive-header-leak-in-proxymanager-low-level-redirects  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-13. Updated: 2026-06-26  
License: CC BY 4.0 with a link back

CVE-2026-44431 · Severity: medium · CVSS 5.3 · Published 2026-05-13

urllib3 is a widely used Python library for making web requests. A security flaw exists where sensitive information, such as login credentials and session cookies, may be unintentionally sent to an untrusted third-party website during a redirect. This could allow an attacker to steal user sessions or authentication tokens if an application uses specific low-level functions of the library.

Technologies: [urllib3 (PyPI)](https://junglewise.ai/threats/technologies/urllib3). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2026-44431 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-44431 being exploited in the wild.

**How severe is CVE-2026-44431?** Medium severity, with a CVSS score of 5.3, published 13 May 2026.

**Which products and versions are affected?** urllib3 (PyPI) >= 1.23, < 2.7.0, ECOSYSTEM:introduced=1.23,fixed=2.7.0.

**Is there a fix for CVE-2026-44431?** Yes. urllib3 (PyPI): upgrade to 2.7.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-44431 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-44431?** Check whether you run urllib3 (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- urllib3 (PyPI): upgrade to 2.7.0 or later

  ```sh
  pip install "urllib3>=2.7.0"
  ```


## Technical details

An information exposure vulnerability exists in urllib3's low-level API. When using ProxyManager.connection_from_url().urlopen() with assert_same_host=False, the library fails to strip sensitive headers (Authorization, Cookie, and Proxy-Authorization) during cross-origin redirects. While the high-level request() API correctly handles these redirects by removing headers defined in Retry.DEFAULT_REMOVE_HEADERS_ON_REDIRECT, the low-level flow bypasses these protections. An attacker who can trigger a redirect to a malicious domain could capture these sensitive headers. The issue is resolved in version 2.7.0.

## Affected products

- urllib3 urllib3 >= 1.23, < 2.7.0

## Identifiers

- CVE-2026-44431
- GHSA-qccp-gfcp-xxvc
- PYSEC-2026-141

## Timeline

- 2026-05-07: advisory: GitHub Security Advisory published
- 2026-05-13: disclosed: CVE published to NVD
- 2026-06-26: patched: Debian LTS security update released

## References

- [https://github.com/urllib3/urllib3/security/advisories/GHSA-qccp-gfcp-xxvc](https://github.com/urllib3/urllib3/security/advisories/GHSA-qccp-gfcp-xxvc)
- [https://lists.debian.org/debian-lts-announce/2026/06/msg00040.html](https://lists.debian.org/debian-lts-announce/2026/06/msg00040.html)

## Related threats

- [urllib3 HTTP client unbounded memory allocation in chunked transfer](https://junglewise.ai/threats/cve-2026-97689-urllib3-is-an-http-client-library-for-python-from-1-10-3-until-2)
- [urllib3 infinite loop in Deflate decoder](https://junglewise.ai/threats/cve-2026-97688-urllib3-is-an-http-client-library-for-python-from-2-6-2-until-2-8)
- [urllib3 HTTPS proxy TLS settings isolation](https://junglewise.ai/threats/cve-2026-97687-urllib3-is-an-http-client-library-for-python-from-1-26-0-until-2)
- [PYSEC-2026-1997 - urllib3 does not control redirects in browsers and Node.js](https://junglewise.ai/threats/cve-2025-50182-urllib3-does-not-control-redirects-in-browsers-and-node-js)
- [PYSEC-2026-1999 - urllib3 redirects are not disabled when retries are disabled on PoolManager instantiation](https://junglewise.ai/threats/cve-2025-50181-urllib3-redirects-are-not-disabled-when-retries-are-disabled-on)