CVE-2026-114613: Unbounded memory leak in msgpack C extension on strict_map_key validation failure
Affects msgpackSource GCVE Database
Not known to be exploited · CVSS 7.5 High : upgrade to 1.2.3 soon.
Data as of 27 Oct 2026, 18:27 UTC
- EPSS
- 0.4% chance of exploitation in 30 days – higher than 38% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 1.2.3
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HExploitation evidence
Disclosed: evidence found.
CVE published 22 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade msgpack to 1.2.3.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| PyPImsgpack | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
A fix is available in msgpack version 1.2.3. Users should upgrade to this version to resolve the memory leak and use-after-free issues. As a temporary workaround, the pure-Python fallback can be used since it does not exhibit the leak, though performance and compatibility should be evaluated. Applying request size and rate limits may reduce but not eliminate memory leakage.
Description
The msgpack-python C extension has a memory leak vulnerability when deserialization rejects a map key with strict_map_key validation enabled (default). This leak occurs because the decoded map value is not released on key validation failure, causing unbounded memory growth and potential denial of service. Additionally, the streaming Unpacker API may suffer from use-after-free issues due to stale parser-stack references. The issue affects msgpack versions prior to 1.2.3 and has been fixed in 1.2.3.
References
- github.com/msgpack/msgpack-python/security/advisories/GHSA-j586-36cw-2gc2 (opens in a new tab)
- nvd.nist.gov/vuln/detail/CVE-2026-114613 (opens in a new tab)
- github.com/msgpack/msgpack-python/commit/620b0eb4c89cd72d4098564537624d9dbb2ce141 (opens in a new tab)
- github.com/msgpack/msgpack-python (opens in a new tab)
- github.com/msgpack/msgpack-python/releases/tag/v1.2.3 (opens in a new tab)