Use-after-free of a server-side SSLContext when sni_callback switches contexts
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.
CVE-2026-19445
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-19445
CPython
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"repo": "https://github.com/python/cpython",
"vendor": "Python Software Foundation",
"modules": [
"ssl"
],
"product": "CPython",
"versions": [
{
"status": "affected",
"version": "0",
"lessThan": "3.10.22",
"versionType": "python"
},
{
"status": "affected",
"version": "3.11.0",
"lessThan": "3.11.17",
"versionType": "python"
},
{
"status": "affected",
"version": "3.12.0",
"lessThan": "3.12.15",
"versionType": "python"
},
{
"status": "affected",
"version": "3.13.0",
"lessThan": "3.13.16",
"versionType": "python"
},
{
"status": "affected",
"version": "3.14.0",
"lessThan": "3.14.8",
"versionType": "python"
},
{
"status": "affected",
"version": "3.15.0a1",
"lessThan": "3.15.0rc3",
"versionType": "python"
}
],
"defaultStatus": "unaffected"
}
]- Related CVEs
- CVE-2026-19445
Source reference:
/cveMetadata/cveId
Publisher severity
critical
Source reference: /containers/cna/metrics
- Event
- #8203 · Revision 1
- Added to Heist Feed
- Publisher date