CVE-2026-19445
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.
- Published Sep 30, 2026
- CVSS 9.2 critical
- 0.4% chance of exploitation in the next 30 days (EPSS)
- A fix is available
Affected software
In the news
- Multiple vulnerabilities in CPython CERT-FR ·