Memory Leak Affecting python-msgpack package, versions <1.2.1-2


Severity

Recommended
low

Based on default assessment until relevant scores are available.

Threat Intelligence

EPSS
0.44% (38th percentile)

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  • Snyk IDSNYK-DEBIANUNSTABLE-PYTHONMSGPACK-21664589
  • published24 Oct 2026
  • disclosed22 Oct 2026

Introduced: 22 Oct 2026

NewCVE-2026-114613  (opens in a new tab)
CWE-401  (opens in a new tab)

How to fix?

Upgrade Debian:unstable python-msgpack to version 1.2.1-2 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream python-msgpack package and not the python-msgpack package as distributed by Debian. See How to fix? for Debian:unstable relevant fixed versions and status.

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 Base Scores

version 3.1