CVE-2026-114613
Published:October 22, 2026
Updated:October 23, 2026
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.
Affected Packages
msgpack-python (CONDA):
Affected version(s) >=1.0.0 <1.2.3Fix Suggestion:
Update to version 1.2.3https://github.com/msgpack/msgpack-python.git (GITHUB):
Affected version(s) >=v1.0.0rc1 <v1.2.3Fix Suggestion:
Update to version v1.2.3msgpack (PYTHON):
Affected version(s) >=1.0.0rc1 <1.2.3Fix Suggestion:
Update to version 1.2.3Related Resources (3)
Do you need more information?
Contact UsCVSS v4
Base Score:
8.7
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
NONE
User Interaction
NONE
Vulnerable System Confidentiality
NONE
Vulnerable System Integrity
NONE
Vulnerable System Availability
HIGH
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
7.5
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Weakness Type (CWE)
Missing Release of Memory after Effective Lifetime