CVE Catalog

CVE-2026-114613

HighCVSS 7.5
Published: Updated: Translated: NVD NIST

Exploitation Probability (EPSS)

Low risk
0.34%

26th percentile - higher than 26% of all known CVEs

Summary

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.

Risk Assessment

Process memory can be exhausted, causing denial of service for applications deserializing untrusted MessagePack data. This can lead to service unavailability and process crashes.

Recommendation

Update msgpack-python to version 1.2.3 or later. Until patched, consider limiting input size and volume and monitoring memory usage.

Related vulnerabilities

Original NVD description (English source)

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.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS