CVE-2025-71343: picklescan - Arbitrary Code Execution via lib2to3.pgen2.pgen.ParserGenerator.make_label Detection Bypass

Severity: high (CVSS 8.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-07-04 · updated 2026-10-12
Weakness: CWE-502

Description

picklescan before 0.0.30 fails to detect malicious pickle files that exploit lib2to3.pgen2.pgen.ParserGenerator.make_label function in the reduce method. Attackers can craft malicious pickle files with embedded code that evades detection but executes arbitrary commands when pickle.load() is called.

Affected products

picklescan: before 0.0.30 — fixed in 0.0.30

How to fix

Upgrade to a fixed version: picklescan 0.0.30. Check the vendor advisory for mitigations.

References

https://github.com/mmaitre314/picklescan/security/advisories/GHSA-p9w7-82w4-7q8m
https://www.vulncheck.com/advisories/picklescan-arbitrary-code-execution-via-lib2to3-pgen2-pgen-parsergenerator-make-label-detection-bypass
https://github.com/mmaitre314/picklescan/security/advisories/GHSA-p9w7-82w4-7q8m

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