Python has added a denylist for known compromised certificates to the ssl module to ensure user safety even without certificate revocation configured. Known compromised certificates will automatically be rejected regardless of the SSLContext policy configuration.
Weakness
The product does not check or incorrectly checks the revocation status of a certificate, which may cause it to use a certificate that has been compromised.
Potential Mitigations
References
- http://www.openwall.com/lists/oss-security/2026/10/20/29
- https://emudhra.we-have-a-problem.com/
- https://github.com/python/cpython/commit/21a50891ab4be2e9955239e625ae2b40c6b1854d
- https://github.com/python/cpython/commit/36cd295f32fc9ba19399e01abee91231440a41dd
- https://github.com/python/cpython/commit/48d9b2712cd52206c7a5882d0fdca4863ed65e93
- https://github.com/python/cpython/commit/7dd8b4736a1419750b94a388e6d158be15836fe6
- https://github.com/python/cpython/commit/98f0e4ed349f370dc8a00366da1a9797e11c9ed5
- https://github.com/python/cpython/commit/a17d9ef549008133eadf20689b1f4787902efe5b
- https://github.com/python/cpython/commit/af52b41afa4330fb38583db553631baa2f122f90
- https://github.com/python/cpython/commit/c7fd7edf7e0d122a3973cf676fae21b6aaa650a8
- https://github.com/python/cpython/commit/e2a9dd97ef9571c710ac0afaa834c8879aebce78
- https://github.com/python/cpython/commit/e4500d8a437ee5b988a5410cb9b59d177aa01370
- https://github.com/python/cpython/commit/e4f63e65a93cf44c14274aa987e644b8c003625e
- https://github.com/python/cpython/commit/e9bf2cf84eebf838a1edaa1c648c2b36345b99d3
- https://github.com/python/cpython/issues/160040
- https://github.com/python/cpython/pull/160042
- https://mail.python.org/archives/list/security-announce@python.org/thread/FNAJMZV6XQYLVPABNINDMF3VF66AYLW4/
- http://www.openwall.com/lists/oss-security/2026/10/24/5