CVE-2024-37891
urllib3's Proxy-Authorization request header isn't stripped during cross-origin redirects
Impact
When using urllib3's proxy support with `ProxyManager`, the `Proxy-Authorization` header is only sent to the configured proxy, as expected. However, when sending HTTP requests *without* using urllib3's proxy support, it's possible to accidentally configure the `Proxy-Authorization` header even though it won't have any effect as the request is not using a forwarding proxy or a tunneling proxy. In those cases, urllib3 doesn't treat the `Proxy-Authorization` HTTP header as one carrying authentication material and thus doesn't strip the header on cross-origin redirects. Because this is a highly unlikely scenario, we believe the severity of this vulnerability is low for almost all users. Out of an abundance of caution urllib3 will automatically strip the `Proxy-Authorization` header during cross-origin redirects to avoid the small chance that users are doing this on accident. Users should use urllib3's proxy support or disable automatic redirects to achieve safe processing of the `Proxy-Authorization` header, but we still decided to strip the header by default in order to further protect users who aren't using the correct approach. ## Affected usages We believe the number of usages affected by this advisory is low. It requires all of the following to be true to be exploited: * Setting the `Proxy-Authorization` header without using urllib3's built-in proxy support. * Not disabling HTTP redirects. * Either not using an HTTPS origin server or for the proxy or target origin to redirect to a malicious origin. ## Remediation * Using the `Proxy-Authorization` header with urllib3's `ProxyManager`. * Disabling HTTP redirects using `redirects=False` when sending requests. * Not using the `Proxy-Authorization` header.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| pip | urllib3 | < 1.26.19 | 1.26.19 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Python | Urllib3 | before 1.26.19 from 2.0.0 before 2.2.2 |
| Debian | Debian Linux | Version 11.0 |
| Netapp | Active Iq Unified Manager | All versions |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/urllib3/urllib3/commit/accff72ecc2f6cf5a76d9570198a93ac7c90270e
- https://github.com/urllib3/urllib3/security/advisories/GHSA-34jh-p97f-mpxf
- https://lists.debian.org/debian-lts-announce/2024/12/msg00020.html
- https://security.netapp.com/advisory/ntap-20240822-0003/
- https://www.vicarius.io/vsociety/posts/proxy-authorization-header-handling-vulnerability-in-urllib3-cve-2024-37891
- https://github.com/advisories/GHSA-34jh-p97f-mpxf
- https://nvd.nist.gov/vuln/detail/CVE-2024-37891
- https://github.com/urllib3/urllib3/commit/40b6d1605814dd1db0a46e202d6e56f2e4c9a468
- https://security.netapp.com/advisory/ntap-20240822-0003