Vulnerability in Python Software Foundation CPython

[ Why it matters ]Priority signals

• Critical severity: CVSS 9.4

[ Description ]Official description

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.

[ Fixes ]Fixes and patches

No fix or interim patch is linked from our sources yet. Check the vendor references below and limit exposure of affected systems until a fix is available.

[ References ]References

• www.openwall.com/lists/oss-security/2026/10/20/29
• emudhra.we-have-a-problem.com
• github.com/python/cpython/commit/21a50891ab4be2e9955239e625ae2b40c6b1854d
• github.com/python/cpython/commit/36cd295f32fc9ba19399e01abee91231440a41dd
• github.com/python/cpython/commit/48d9b2712cd52206c7a5882d0fdca4863ed65e93
• github.com/python/cpython/commit/7dd8b4736a1419750b94a388e6d158be15836fe6
• github.com/python/cpython/commit/98f0e4ed349f370dc8a00366da1a9797e11c9ed5
• github.com/python/cpython/commit/a17d9ef549008133eadf20689b1f4787902efe5b
• github.com/python/cpython/commit/af52b41afa4330fb38583db553631baa2f122f90
• github.com/python/cpython/commit/c7fd7edf7e0d122a3973cf676fae21b6aaa650a8
• github.com/python/cpython/commit/e2a9dd97ef9571c710ac0afaa834c8879aebce78
• github.com/python/cpython/commit/e4500d8a437ee5b988a5410cb9b59d177aa01370
• github.com/python/cpython/commit/e4f63e65a93cf44c14274aa987e644b8c003625e
• github.com/python/cpython/commit/e9bf2cf84eebf838a1edaa1c648c2b36345b99d3
• github.com/python/cpython/issues/160040
• github.com/python/cpython/pull/160042
• mail.python.org/archives/list/security-announce@python.org/thread/FNAJMZV6XQYLVPABNINDM…
• www.openwall.com/lists/oss-security/2026/10/24/5