CVE-2026-114613
MessagePack: Unbounded memory leak in msgpack C extension on strict_map_key validation failure
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.
INFO
Published Date :
Oct. 22, 2026, 7:17 p.m.
Last Modified :
Oct. 22, 2026, 7:17 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | HIGH | MITRE-CVE | ||||
| CVSS 3.1 | HIGH | [email protected] |
Solution
- Update msgpack-python to version 1.2.3 or later.
- Ensure strict_map_key is set if using older versions.
- Monitor application memory usage closely.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-114613.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-114613 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-114613
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-114613 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-114613 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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New CVE Received by [email protected]
Oct. 22, 2026
Action Type Old Value New Value Added 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. Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Added CWE CWE-401 Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/114xxx/CVE-2026-114613.json">CVE-2026-114613</a> Added Reference https://github.com/msgpack/msgpack-python/commit/620b0eb4c89cd72d4098564537624d9dbb2ce141 Added Reference https://github.com/msgpack/msgpack-python/releases/tag/v1.2.3 Added Reference https://github.com/msgpack/msgpack-python/security/advisories/GHSA-j586-36cw-2gc2