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CVE PROGRAM SOURCE RECORD9.2 Critical

CVE-2026-19445

Use-after-free of a server-side SSLContext when sni_callback switches contexts

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Status
Published
Published
Updated
Assigning organization
PSF

Description

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.

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Python Software Foundation CPython

Default version status: unaffected

  • 0 to < 3.10.22affected
  • 3.11.0 to < 3.11.17affected
  • 3.12.0 to < 3.12.15affected
  • 3.13.0 to < 3.13.16affected
  • 3.14.0 to < 3.14.8affected
  • 3.15.0a1 to < 3.15.0rc3affected

References