The HTTPPasswordMgr class in the urllib.request module, along with its subclasses HTTPPasswordMgrWithDefaultRealm and HTTPPasswordMgrWithPriorAuth, did not take the URL scheme into account when matching stored credentials against a requested URL. Credentials added for an https:// URL were also used for requests to the same host over http://, so an attacker able to redirect or downgrade a client to plain HTTP (for example, via an HTTPS-to-HTTP redirect or an on-path position) could capture credentials in cleartext. Credentials added for http:// URLs could likewise be sent over https://.
Credential matching is now scoped by URL scheme. Credentials registered with a URL that includes a scheme are only used for requests with the same scheme. Credentials registered with a bare authority (such as example.com or example.com:8080) continue to match any scheme, preserving compatibility with existing code, including proxy authentication.
Users who cannot upgrade immediately can mitigate by ensuring that applications never make plain http:// requests to hosts for which credentials are registered, for example by not following redirects to http:// URLs.
Weakness
The product transmits sensitive or security-critical data in cleartext in a communication channel that can be sniffed by unauthorized actors.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Red Hat Hardened Images | RedHat | python3-14-main-3.14.7-1.1.hum1 | * |
| Red Hat Hardened Images | RedHat | python3-10-main-3.10.21-1.1.hum1 | * |
| Red Hat Hardened Images | RedHat | python3-11-main-3.11.16-1.2.hum1 | * |
| Red Hat Hardened Images | RedHat | python3-12-main-3.12.14-1.1.hum1 | * |
| Red Hat Hardened Images | RedHat | python3-13-main-3.13.15-1.1.hum1 | * |
Potential Mitigations
Related Attack Patterns
- https://cwe.mitre.org/data/definitions/102.html
- https://cwe.mitre.org/data/definitions/117.html
- https://cwe.mitre.org/data/definitions/383.html
- https://cwe.mitre.org/data/definitions/477.html
- https://cwe.mitre.org/data/definitions/65.html
References
- https://github.com/python/cpython/commit/641be42bb07921ba0f8bffe228b1dc706b092ef6
- https://github.com/python/cpython/commit/851cf9a7142ecbdd39f831055533f58284ad2bcc
- https://github.com/python/cpython/commit/95355ee3a8e1d3c3d4858d1973aa42a9b91a2801
- https://github.com/python/cpython/commit/a0d023fbd23773e24b35d8368789470e22cda5d8
- https://github.com/python/cpython/commit/a2773a34183b7d94a243bb98fd658926cc5348ce
- https://github.com/python/cpython/commit/a7bb524fef61f77ede01f660ffbd591e1d5837ce
- https://github.com/python/cpython/commit/dac88d8615078c55f1304ea4c7a2d822700d4e5a
- https://github.com/python/cpython/issues/155694
- https://github.com/python/cpython/pull/155696
- https://mail.python.org/archives/list/security-announce@python.org/thread/3OKPE5S75KDNA7FY7AI3PL2MXM2X5RB3/
- http://www.openwall.com/lists/oss-security/2026/08/18/3
- https://github.com/python/cpython/issues/155694