CVE-2026-114613: CWE-401: Missing Release of Memory after Effective Lifetime in msgpack msgpack-python
Description
CVE-2026-114613 is a high-severity vulnerability in the msgpack-python library prior to version 1.2.3. It involves a memory leak in the C extension (msgpack._cmsgpack) when deserializing MessagePack data with strict_map_key=True, the default setting. This leak occurs if a key is rejected during deserialization, leading to unbounded memory growth and potential denial of service. Both the unpackb() function and the streaming Unpacker API are affected. The pure-Python fallback implementation is not affected. The issue is fixed in version 1.2.3.
CVSS v3.1
Score 7.5high
Affected software
msgpack
msgpack-python
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability in msgpack-python (CVE-2026-114613) is due to missing release of memory after its effective lifetime in the C extension module msgpack._cmsgpack. When deserialization rejects a map key under strict_map_key=True, the decoded map value is leaked. This memory leak can be triggered repeatedly by malformed inputs, causing unbounded process memory growth and denial of service. Both the unpackb() function and the streaming Unpacker API are impacted. The pure-Python fallback does not exhibit this leak. The issue is resolved in msgpack-python version 1.2.3.
Potential Impact
Exploitation of this vulnerability can cause unbounded memory growth in applications using vulnerable versions of msgpack-python when deserializing attacker-controlled MessagePack data with strict_map_key enabled. This can lead to denial of service due to resource exhaustion. There is no impact on confidentiality or integrity, only availability is affected.
Mitigation Recommendations
Upgrade msgpack-python to version 1.2.3 or later, where this memory leak issue has been fixed. No other mitigation is necessary as the vulnerability is fully addressed by this official fix.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-10-21T20:34:25.599Z
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 6ada59f44d27ba8daa722193
Added to database: 10/22/2026, 18:46:12 UTC
Last enriched: 10/22/2026, 19:00:20 UTC
Last updated: 10/22/2026, 19:01:08 UTC
Views: 5
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