CVE-2026-19445Use-after-free of a server-side SSLContext when sni_callback switches contexts
Updated under an hour ago ()
Does this affect you?
It affects Python Software Foundation CPython. Add what you run to find out whether that includes you.
EPSS puts the chance of exploitation in the next 30 days at 0.43%, higher than 35% of scored CVEs.
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A remote, unauthenticated TLS client can make a server crash or call through a freed pointer if its sni_callback assigns a different context to SSLSocket.context (the documented way to select a certificate per server name) and nothing else keeps the original ssl.SSLContext alive. Typical cases are servers that create an SSLContext per connection or replace it while connections are open; servers that wrap their listening socket with it are not affected. Mitigation: keep a reference to every SSLContext that sets sni_callback for the lifetime of the server. TLS clients are not affected.
- CVSS
- 9.2 CRITICAL (v4.0, CNA)CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N
- Weakness (CWE)
- CWE-416
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- 0.43% (percentile 35)
- Assigned by
- PSF
- NVD analysis
- Awaiting Analysis
- Record last updated
- Oct 3, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
Python Software Foundation CPython python_software_foundation:cpython (from the name) | before 3.10.22; from 3.11.0 before 3.11.17; from 3.12.0 before 3.12.15; from 3.13.0 before 3.13.16; from 3.14.0 before 3.14.8; from 3.15.0a1 before 3.15.0rc3 | CNA record |
References
- https://github.com/python/cpython/pull/158504patch
- https://mail.python.org/archives/list/security-announce@python.org/thread/QMQIUQB6WGGC3MI7I3WKQXOYOBDSPPS3/vendor-advisory
- https://github.com/python/cpython/issues/156293issue-tracking
- https://github.com/python/cpython/commit/34a53dce8174da2fceb12fe084a4def02a10053dpatch
- https://github.com/python/cpython/commit/46133cd57d309652139ada74014aca7665ac552bpatch
- https://github.com/python/cpython/commit/63fab143d94cafae71850831acfb52041ba44af7patch
- https://github.com/python/cpython/commit/cd7e51e7d4563866fbaa1e2521ae69b45daf3698patch
- https://github.com/python/cpython/commit/d8717ed01717a9641686e6e6f83f0ab8af235e2cpatch
- https://github.com/python/cpython/commit/b12968cefe69ca1dcb8606c832ff73ee7dbf4ba8patch
- https://github.com/python/cpython/commit/ec44b5a3258cbda947d5e07242ee562ed05ef24bpatch
- http://www.openwall.com/lists/oss-security/2026/09/30/17
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.