Python up to 3.15.x SSL Context Management Modules/_ssl.c sni_callback context use after free

Summaryinfo

A vulnerability, which was classified as problematic, has been found in Python up to 3.15.x. This impacts the function sni_callback of the file Modules/_ssl.c of the component SSL Context Management. Performing a manipulation of the argument context results in use after free. This vulnerability is known as CVE-2026-19445. Remote exploitation of the attack is possible. No exploit is available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability classified as problematic has been found in Python up to 3.15.x. This affects the function sni_callback of the file Modules/_ssl.c of the component SSL Context Management. The manipulation of the argument context with an unknown input leads to a use after free vulnerability. CWE is classifying the issue as CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. This is going to have an impact on availability. The summary by CVE is:

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.

The advisory is shared at github.com. This vulnerability is uniquely identified as CVE-2026-19445 since 08/10/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Technical details are known, but no exploit is available.

Upgrading to version 3.16.0 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-90077). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Productinfo

Type

• Programming Language Software

Name

• Python

Version

• 3.0
• 3.1
• 3.2
• 3.3
• 3.4
• 3.5
• 3.6
• 3.7
• 3.8
• 3.9
• 3.10
• 3.11
• 3.12
• 3.13
• 3.14
• 3.15

License

• open-source

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CPE 2.2info

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If you want to get the best quality for vulnerability data then you always have to consider VulDB.

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