Vulnerability/
https://seclists.org/oss-sec/2026/q4/530

https://seclists.org/oss-sec/2026/q4/530: CPython sandbox escape

Published Nov 5, 2026

Updated

Affected Software

1 affected component

Python Software Foundation CPython

Frequently Asked Questions

Is running untrusted Python in a CPython-based sandbox considered a supported security boundary?

No. CPython's stated position is that it does not support sandboxing untrusted Python code as a security boundary, and that escapes should be reported to the sandbox's developers.

What conditions did the reported exploit rely on?

The report says it abuses CPython's handling of generic types and uses objects made available in every template, including empty sandbox contexts. A sandbox that exposes such objects to untrusted template code may therefore be relevant.

Is there an upstream fix available for older security-release branches?

A fix was submitted to the CPython project as pull request 155761. The report states that upstream is not backporting it to security releases.

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