---
tags:
  - vulnerability-poc
  - rce
  - messagepack
---

# Vulnerability Disclosure: Critical RCE in MessagePack

## Overview
This repository contains a proof-of-concept (PoC) for an Arbitrary Code Execution (ACE) vulnerability identified in the `MessagePack` deserialization process.

## Target Format
`.msgpack`

## Description
The application utilizes `msgpack.unpack()` on untrusted model/data files without strict type validation. By crafting a payload using MessagePack extension types, an attacker can instantiate and execute arbitrary system commands during the deserialization process.

## Proof of Concept
The provided `poc_messagepack.msgpack` triggers `os.system('echo ACE_TRIGGERED')`.

## Steps to Reproduce
1. Install a vulnerable version of the target parser/library.
2. Execute the loader:
   ```python
   import msgpack
   with open("poc_messagepack.msgpack", "rb") as f:
       msgpack.unpack(f)
   ```
3. Observe the execution of the command.

## Recommendation
Implement a strict allow-list for deserialized objects or transition to non-executable serialization formats.

## Security Impact
Full remote code execution on the host machine during the model loading phase.