# Unsafe MessagePack Deserialization

> Detects MessagePack deserialization configured to allow arbitrary object construction.

- Skill: `zakirkun/unsafe-messagepack-deserialization` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add zakirkun/unsafe-messagepack-deserialization`
- Raw SKILL.md: https://api.skillmd.com/api/skills/zakirkun/unsafe-messagepack-deserialization/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: zakirkun (https://skillmd.com/u/zakirkun)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/zakirkun/unsafe-messagepack-deserialization

---


# Unsafe MessagePack Deserialization

## Overview
MessagePack is generally safer than pickle/Java serialization, but certain configurations and extensions can allow type coercion or code execution when combined with object extensibility features.

## Remediation
- Use `raw=True` in Python msgpack to avoid string coercion
- Validate deserialized data against a schema before use
- Do not pass deserialized objects directly to code execution paths