CVE-2025-50182

MEDIUM5.3EPSS 0.07%

urllib3 does not control redirects in browsers and Node.js

Published: 6/18/2025Modified: 2/4/2026
Also known as:GHSA-48p4-8xcf-vxj5CGA-5662-r5jm-85prDEBIAN-CVE-2025-50182

Description

urllib3 [supports](https://urllib3.readthedocs.io/en/2.4.0/reference/contrib/emscripten.html) being used in a Pyodide runtime utilizing the [JavaScript Fetch API](https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API) or falling back on [XMLHttpRequest](https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest). This means you can use Python libraries to make HTTP requests from your browser or Node.js. Additionally, urllib3 provides [a mechanism](https://urllib3.readthedocs.io/en/2.4.0/user-guide.html#retrying-requests) to control redirects. However, the `retries` and `redirect` parameters are ignored with Pyodide; the runtime itself determines redirect behavior. ## Affected usages Any code which relies on urllib3 to control the number of redirects for an HTTP request in a Pyodide runtime. ## Impact Redirects are often used to exploit SSRF vulnerabilities. An application attempting to mitigate SSRF or open redirect vulnerabilities by disabling redirects may remain vulnerable if a Pyodide runtime redirect mechanism is unsuitable. ## Remediation If you use urllib3 in Node.js, upgrade to a patched version of urllib3. Unfortunately, browsers provide no suitable way which urllib3 can use: `XMLHttpRequest` provides no control over redirects, the Fetch API returns `opaqueredirect` responses lacking data when redirects are controlled manually. Expect default browser behavior for redirects.

Affected packages (2)

CVSS scores

SourceVersionSeverityVector
osvCVSS 3.1MEDIUM5.3CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N

References (6)