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.
References10
- www.openwall.com/lists/oss-security/2026/10/20/29
- emudhra.we-have-a-problem.com/
- github.com/python/cpython/commit/21a50891ab4be2e9955239e625ae2b…
- github.com/python/cpython/commit/36cd295f32fc9ba19399e01abee912…
- github.com/python/cpython/commit/48d9b2712cd52206c7a5882d0fdca4…
- github.com/python/cpython/commit/7dd8b4736a1419750b94a388e6d158…
- github.com/python/cpython/commit/98f0e4ed349f370dc8a00366da1a97…
- github.com/python/cpython/commit/a17d9ef549008133eadf20689b1f47…
- github.com/python/cpython/commit/af52b41afa4330fb38583db553631b…
- github.com/python/cpython/commit/c7fd7edf7e0d122a3973cf676fae21…
Metrics
- CVSS 4.0
-
9.4
CRITICAL
Score source: CNA
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - EPSS — exploit probability
- 1% percentile: 45 · as of 8 November 2026
- CWE
- CWE-299
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.