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

> Attackers can bypass picklescan detection to execute arbitrary code via malicious pickle payloads using lib2to3 grammar loading.

- **Severity:** High 7.6 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 4 Jul 2026
- **Updated:** 6 Jul 2026
- **Also known as:** GHSA-f54q-57x4-jg88, GHSA-vp8m-mf3r-82q9

## What is CVE-2025-71359?

CVE-2025-71359 is a high-severity unsafe deserialization vulnerability in picklescan, published on 4 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official 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.

Weakness: CWE-502 (Deserialization of Untrusted Data)

## Which versions are affected by CVE-2025-71359?

2 open source packages ship an affected version, including picklescan.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `picklescan` | PyPI | All versions | 0.0.29 |
| `picklescan` | PyPI | All versions | 0.0.29 |

## How do I fix CVE-2025-71359?

Upgrade picklescan to 0.0.29 or later.

## Is CVE-2025-71359 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-71359 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-71359 and fix it if it is affected.

What it is: CVE-2025-71359 is a high-severity unsafe deserialization vulnerability in picklescan, published on 4 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-71359 exists.

Affected packages and fixed versions:
- picklescan (PyPI): affected all versions; fixed in 0.0.29
- picklescan (PyPI): affected all versions; fixed in 0.0.29

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2025-71359/ (Markdown: https://insights.sbomify.com/CVE-2025-71359/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-71359
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-71359
- OSV: https://osv.dev/vulnerability/CVE-2025-71359

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-71359/
Summaries are generated and may contain mistakes; the official description above is the record.