Python ssl module denylists compromised intermediates (CVE-2026-115557)
The notice says the denylist should protect users even when those certificates are not yet removed elsewhere.
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CVE-2026-115557
Python ssl does not reject known compromised certificates
- CVSS 4.0
- 9.4 critical
- EPSS
- —
- Published
- ·
- Modified
AI analysisSummaries by Vani AI
Python's ssl module did not automatically reject known compromised certificates unless certificate revocation was configured. A remote attacker holding a compromised intermediate certificate can impersonate a TLS peer when a user connects, with no privileges required. Python applications and runtimes that rely on ssl without revocation checks are affected.
What to do: Upgrade to a Python release that adds the ssl denylist for known compromised certificates. No workaround is documented.
| Product | Affected |
|---|---|
| Python ssl module | — |
Estimated exposure
No basis for an estimate.
Order-of-magnitude estimate by the model from install counts, market share and public scan data it knows; verify before quoting.
Description · NVD
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
- CWE-299
- Vector
- 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