willardj/msgpack-numpy-rce-poc

msgpack-numpy RCE PoC (CWE-502)

DO NOT LOAD THIS FILE IN AN UNCONTROLLED ENVIRONMENT

This repository contains a proof-of-concept .msgpack file that demonstrates arbitrary code execution via msgpack_numpy.unpackb().

Vulnerability

msgpack_numpy.decode() at line 99-100 calls pickle.loads(obj[b'data']) with zero validation when obj[b'kind'] == b'O'. An attacker who distributes a crafted .msgpack file causes any victim process that loads it with msgpack_numpy.unpackb() to execute arbitrary code.

Reproduction

import msgpack_numpy
import msgpack

data = open("malicious.msgpack", "rb").read()
msgpack_numpy.unpackb(data, raw=False)  # RCE triggers here
# Creates /tmp/msgpack-rce-proof.txt with content "EXPLOITED"

Affected

• msgpack-numpy 0.4.8 (latest, all versions affected)
• 842,000 monthly PyPI downloads
• Unmaintained since July 2024