{"id":"CVE-2026-114613","published":"2026-10-22T19:17:37.733","lastModified":"2026-10-23T21:17:21.823","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.","cvssScore":7.5,"cvssSeverity":"HIGH","cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","cwes":["CWE-401"],"vendors":[],"products":[],"references":[{"url":"https://github.com/msgpack/msgpack-python/commit/620b0eb4c89cd72d4098564537624d9dbb2ce141","tags":[]},{"url":"https://github.com/msgpack/msgpack-python/releases/tag/v1.2.3","tags":[]},{"url":"https://github.com/msgpack/msgpack-python/security/advisories/GHSA-j586-36cw-2gc2","tags":[]}],"exploitRefs":[{"url":"https://github.com/msgpack/msgpack-python/commit/620b0eb4c89cd72d4098564537624d9dbb2ce141","tags":[]},{"url":"https://github.com/msgpack/msgpack-python/releases/tag/v1.2.3","tags":[]},{"url":"https://github.com/msgpack/msgpack-python/security/advisories/GHSA-j586-36cw-2gc2","tags":[]}],"hasPoc":true,"ai":null}