---
title: "CVE-2026-114613: MessagePack Python - Denial of Service"
description: "MessagePack Python serializer prior to 1.2.3 contains a denial of service caused by memory leak in msgpack._cmsgpack when deserialization rejects keys with strict_map_key=True, letting attackers cause unbounded memory growth via crafted inputs, exploit requires attacker-controlled MessagePack data."
url: https://panop.io/threat-heartbeat/CVE-2026-114613/
---

# CVE-2026-114613 MessagePack Python - Denial of Service

MessagePack Python serializer prior to 1.2.3 contains a denial of service caused by memory leak in msgpack.\_cmsgpack when deserialization rejects keys with strict\_map\_key=True, letting attackers cause unbounded memory growth via crafted inputs, exploit requires attacker-controlled MessagePack data.

CVSS base score 7.5 /10

High

CISA KEV

Not listed

Public exploit

None known

Authentication

Not required

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-114613)

## Details

Type

Denial of Service

Impact

Denial Of Service

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Published

22 October 2026

Updated

23 October 2026

Weakness

[CWE-401](https://cwe.mitre.org/data/definitions/401.html)

## Vendor fix

Upgrade to version 1.2.3 or later.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

## References

- [https://nvd.nist.gov/vuln/detail/CVE-2026-114613](https://nvd.nist.gov/vuln/detail/CVE-2026-114613)
- [https://github.com/msgpack/msgpack-python/commit/620b0eb4c89cd72d4098564537624d9dbb2ce141](https://github.com/msgpack/msgpack-python/commit/620b0eb4c89cd72d4098564537624d9dbb2ce141)
- [https://github.com/msgpack/msgpack-python/releases/tag/v1.2.3](https://github.com/msgpack/msgpack-python/releases/tag/v1.2.3)
- [https://github.com/msgpack/msgpack-python/security/advisories/GHSA-j586-36cw-2gc2](https://github.com/msgpack/msgpack-python/security/advisories/GHSA-j586-36cw-2gc2)

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## What this record can't tell you

- Whether you run the affected software, and where
- Whether an attacker can actually reach and exploit it
- The misconfigurations that never get a CVE number
- What it would cost the business, ranked into what to fix first

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