Vulnerability Description
MessagePack is the serializer implementation for Python msgpack.org. Prior to 1.2.3, the msgpack-python C extension (msgpack._cmsgpack) leaks a decoded map value when deserialization rejects a key with strict_map_key=True (the default). Repeated malformed inputs can cause unbounded process memory growth and denial of service in applications that deserialize attacker-controlled MessagePack data. Both unpackb() and the streaming Unpacker API are affected. The pure-Python fallback does not exhibit this leak in the reported tests. This issue is fixed in version 1.2.3.
CVSS Score
HIGH
Related Weaknesses (CWE)
References
- https://github.com/msgpack/msgpack-python/commit/620b0eb4c89cd72d4098564537624d9
- https://github.com/msgpack/msgpack-python/releases/tag/v1.2.3
- https://github.com/msgpack/msgpack-python/security/advisories/GHSA-j586-36cw-2gc
FAQ
What is CVE-2026-114613?
CVE-2026-114613 is a vulnerability with a CVSS score of 7.5 (HIGH). MessagePack is the serializer implementation for Python msgpack.org. Prior to 1.2.3, the msgpack-python C extension (msgpack._cmsgpack) leaks a decoded map value when deserialization rejects a key wit...
How severe is CVE-2026-114613?
CVE-2026-114613 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-114613?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.