Improper certificate revocation check in CPython ssl module
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- Passive
- Attack complexity
- Low
- Attack requirements
- None
- Impact type
- —
- Confidentiality · integrity · availability
- High · High · High
- Fix status
- Partial Red Hat: 10 without a fix
Attack profile from CVSS 4.0 · CNA. Fix status from CNA and Red Hat.
Summary
CPython versions before 3.11.18, from 3.12.0 before 3.12.16, from 3.13.0 before 3.13.18, from 3.14.0 before 3.14.10, from 3.15.0 before 3.15.2 and from 3.16.0a1 before 3.16.0 are affected. The ssl module accepts known compromised certificates when certificate revocation checking is not configured (CWE-299). A remote attacker with a compromised certificate can exploit this without privileges, though user interaction is required.
Written with Claude Haiku 5.5 from the sources below · 2026-11-07
Description from the CNA
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.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Total
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Python Software Foundation | CPython | before 3.11.18; 3.12.0 to before 3.12.16; 3.13.0 to before 3.13.18; 3.14.0 to before 3.14.10; 3.15.0 to before 3.15.2; 3.16.0a1 to before 3.16.0 | 3.11.18, 3.12.16, 3.13.18, 3.14.10, 3.15.2, 3.16.0 | Patch available | CNA |
- CPython VendorPython Software Foundation Affected before 3.11.18; 3.12.0 to before 3.12.16; 3.13.0 to before 3.13.18; 3.14.0 to before 3.14.10; 3.15.0 to before 3.15.2; 3.16.0a1 to before 3.16.0 Fixed in 3.11.18, 3.12.16, 3.13.18, 3.14.10, 3.15.2, 3.16.0 Patch available CNA
CPE names Threatist (inferred) · 1
Inferred from how NVD named this product before; not given by a source.
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:python:python:*:*:*:*:*:*:*:* | — | — | python-pillow |
- cpe:2.3:a:python:python:*:*:*:*:*:*:*:* Versions — — ·python-pillow
Remediation
Update CPython to 3.11.18, 3.12.16, 3.13.18, 3.14.10, 3.15.2 or 3.16.0, matching the branch in use. Red Hat lists Red Hat Enterprise Linux 6 and 7 as affected with no fix planned, and Red Hat Enterprise Linux 8, 9 and 10, Red Hat Enterprise Linux AI (RHEL AI) 3, Red Hat Hardened Images, Red Hat OpenShift Virtualization 4 and 5, and Self-service automation portal 2 as affected with plan none available.
Written with Claude Haiku 5.5 from the sources below · 2026-11-07
- Fix · CNA CPython (Python Software Foundation) Fixed in 3.11.18, 3.12.16, 3.13.18, 3.14.10, 3.15.2, 3.16.0
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Enterprise Linux 10 | Affected | No fix yet |
| Red Hat Enterprise Linux 6 | Affected | No fix planned: Out of support scope |
| Red Hat Enterprise Linux 7 | Affected | No fix planned: Out of support scope |
| Red Hat Enterprise Linux 8 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 9 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux AI (RHEL AI) 3 | Affected | No fix yet: Fix deferred |
| Red Hat Hardened Images | Affected | No fix yet |
| Red Hat OpenShift Virtualization 4 | Affected | No fix yet: Fix deferred |
| Red Hat OpenShift Virtualization 5 | Affected | No fix yet: Fix deferred |
| Self-service automation portal 2 | Affected | No fix yet: Fix deferred |
Not affected: 2 products
- Red Hat Enterprise Linux 8
- Red Hat Hardened Images
Timeline
- 2026-10-24 Threatist record created from CVE-2026-115557
- 2026-10-24 Alias added: GHSA-x547-2835-q547
- 2026-10-25 Fix available: Python Software Foundation/[email protected] · CNA
- 2026-10-25 12 new references · CNA
- 2026-10-26 Fix available: Python Software Foundation/[email protected], Python Software Foundation/[email protected], Python Software Foundation/[email protected] · CNA
- 2026-10-27 Fix available: Python Software Foundation/[email protected], Python Software Foundation/[email protected] · CNA
- 2026-11-02 CISA SSVC decision points changed
- 2026-11-04 Affected versions changed · Red Hat
- 2026-11-04 CVSS score added · Red Hat
- 2026-11-05 Affected versions changed · Red Hat
- 2026-11-07 Affected versions changed · Red Hat
References
Patch 13
- https://github.com/python/cpython/pull/160042
- 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
Advisory 2
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- TI-2024-07037 Quadratic complexity parsing cookies with backslashes CVSS 3.1HIGH 7.5
- TI-2024-11791 Bypass extraction filter to modify file metadata outside extraction directory CVSS 3.1MEDIUM 5.3
- TI-2024-00411 Quoted zip-bomb protection for zipfile CVSS 3.1MEDIUM 6.2
- TI-2026-13296 `HTTPPasswordMgr` can send saved HTTPS credentials via HTTP because of incorrect scheme matching CVSS 4.0MEDIUM 6.0
- TI-2024-06422 Email header injection due to unquoted newlines CVSS 3.1MEDIUM 5.5
- TI-2026-04606 Possible to hijack modules in current working directory CVSS 4.0MEDIUM 5.6
Sources
- CVE-2026-115557 · CVE Program
- CVE-2026-115557 · NVD
- FIRST EPSS
- GHSA-x547-2835-q547 · GitHub Advisory Database · CC BY 4.0
- CVE-2026-115557 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences