{"id":"PYSEC-2026-1997","summary":"urllib3 does not control redirects in browsers and Node.js","details":"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.\n\nHowever, the `retries` and `redirect` parameters are ignored with Pyodide; the runtime itself determines redirect behavior.\n\n\n## Affected usages\n\nAny code which relies on urllib3 to control the number of redirects for an HTTP request in a Pyodide runtime.\n\n\n## Impact\n\nRedirects 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.\n\n\n## Remediation\n\nIf you use urllib3 in Node.js, upgrade to a patched version of urllib3.\n\nUnfortunately, 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.","aliases":["CVE-2025-50182","GHSA-48p4-8xcf-vxj5"],"modified":"2026-07-07T17:48:15.745179657Z","published":"2026-07-07T16:02:55.593591Z","references":[{"type":"WEB","url":"https://github.com/urllib3/urllib3/security/advisories/GHSA-48p4-8xcf-vxj5"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-50182"},{"type":"FIX","url":"https://github.com/urllib3/urllib3/commit/7eb4a2aafe49a279c29b6d1f0ed0f42e9736194f"},{"type":"PACKAGE","url":"https://github.com/urllib3/urllib3"},{"type":"WEB","url":"https://github.com/urllib3/urllib3/releases/tag/2.5.0"},{"type":"PACKAGE","url":"https://pypi.org/project/urllib3"},{"type":"ADVISORY","url":"https://github.com/advisories/GHSA-48p4-8xcf-vxj5"}],"affected":[{"package":{"name":"urllib3","ecosystem":"PyPI","purl":"pkg:pypi/urllib3"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"2.2.0"},{"fixed":"2.5.0"}]}],"versions":["2.2.0","2.2.1","2.2.2","2.2.3","2.3.0","2.4.0"],"database_specific":{"source":"https://github.com/pypa/advisory-database/blob/main/vulns/urllib3/PYSEC-2026-1997.yaml"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N"}]}