CVE-2026-115557
Python has added a denylist for known compromised certificates to the "ssl" module to ensure user safety even without certificate revocation configured.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.53%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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.
- CVSS 4.0
- 9.4 CRITICALCVSS: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/M
- EPSS
- 0.53% probability · 45th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-299
- Source
- cna@python.org
EPSS moved from 0.5% on 25 October 2026 to 0.5% on 26 October 2026.
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
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.