CVE-2026-57585

Name	CVE-2026-57585
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.
Source	CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
python-msgpack (PTS)	bullseye	1.0.0-6	vulnerable
	bookworm	1.0.3-2	vulnerable
	trixie	1.0.3-3	vulnerable
	forky, sid	1.1.2-2	vulnerable

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
python-msgpack	source	(unstable)	(unfixed)

Notes

https://github.com/msgpack/msgpack-python/security/advisories/GHSA-6v7p-g79w-8964
Fixed by: https://github.com/msgpack/msgpack-python/commit/2c56ddb5d0025ed481d962c0f5d62d19dec7476d (v1.2.1)