CVE-2025-71359: picklescan - Unsafe Deserialization via lib2to3.pgen2.grammar.Grammar.loads

Severity: high (CVSS 8.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% 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 0.0.29 fails to detect malicious pickle payloads that utilize lib2to3.pgen2.grammar.Grammar.loads in the reduce method, allowing remote code execution. Attackers can craft pickle files embedding dangerous code that evades picklescan detection and executes during pickle.load() deserialization.

Affected products

picklescan: before 0.0.29 — fixed in 0.0.29

How to fix

Upgrade to a fixed version: picklescan 0.0.29. Check the vendor advisory for mitigations.

References

https://github.com/mmaitre314/picklescan/security/advisories/GHSA-f54q-57x4-jg88
https://www.vulncheck.com/advisories/picklescan-unsafe-deserialization-via-lib2to3-pgen2-grammar-grammar-loads
https://github.com/mmaitre314/picklescan/security/advisories/GHSA-f54q-57x4-jg88

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