CVE-2026-57585

MessagePack: Out-of-bounds read/crash on Unpacker reuse after caught error

State: Published
Severity: 7.5 High
Published: Jun 30, 2026
Updated: Jul 1, 2026
Reserved: Jun 24, 2026

Description

MessagePack is the serializer implementation for Python msgpack.org. Prior to 1.2.1, there is an Out-of-bounds read/crash on Unpacker reuse after a caught error, potentially leading to a DoS attack. If the Unpacker is used repeatedly after an error occurs, the process may crash with a SEGV. This issue has been fixed in version 1.2.1.

Scores

CVSS	Score	Vector	Source
3.1	7.5 High	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H	GitHub_M

Weaknesses

CWE-416 Use After Free

Affected Products

Product	Versions
msgpack-pythonmsgpack	< 1.2.1Affected

References

https://github.com/msgpack/msgpack-python/security/advisories/GHSA-6v7p-g79w-8964
https://github.com/msgpack/msgpack-python/commit/2c56ddb5d0025ed481d962c0f5d62d19dec7476d

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