CVE-2026-114613MessagePack: Unbounded memory leak in msgpack C extension on strict_map_key validation failure
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It affects msgpack-python. Add what you run to find out whether that includes you.
EPSS puts the chance of exploitation in the next 30 days at 0.44%, higher than 38% of scored CVEs.
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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
- 7.5 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Weakness (CWE)
- CWE-401
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- 0.44% (percentile 38)
- Assigned by
- GitHub_M
- NVD analysis
- Awaiting Analysis
- Record last updated
- Oct 23, 2026
- First seen by InfoSec Signals
- Oct 22, 2026
The CVE record on cve.org NVD's entry
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