CVE-2025-50182: 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 you can use Python libraries to make HTTP requests from your browser or Node.js. Additionally, urllib3 provides a mechanism 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.
Other sources
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.
— NVD
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
pip/urllib3to a version that resolves this vulnerability.Fixed in 2.5.0 - Upgrade
Upgrade
urllib3to a version that resolves this vulnerability.Fixed in 2.5.0 - Compensating control
In a Pyodide runtime, do not rely on urllib3 `retries` or redirect-related parameters to prevent SSRF/open-redirect behavior because Pyodide ignores urllib3 redirect/retry controls and the runtime determines redirect behavior; design mitigations that do not depend on disabling redirects via urllib3 in Pyodide, and account for default browser redirect behavior.
Event History
Frequently Asked Questions
What is the severity of CVE-2025-50182?
CVE-2025-50182 is classified as a moderate severity vulnerability.
How do I fix CVE-2025-50182?
To fix CVE-2025-50182, upgrade urllib3 to version 2.5.0 or later.
Which versions of urllib3 are affected by CVE-2025-50182?
CVE-2025-50182 affects versions of urllib3 below 2.5.0.
What types of applications are impacted by CVE-2025-50182?
CVE-2025-50182 impacts applications using urllib3 in a Pyodide runtime environment.
Is CVE-2025-50182 a local or remote vulnerability?
CVE-2025-50182 is considered a remote vulnerability as it can be exploited over the network.