CVE-2026-54522

Name	CVE-2026-54522
Description	MessagePack for Ruby is an implementation of the MessagePack binary serialization format. Prior to 1.8.2, MessagePack::Buffer#clear in ext/msgpack/buffer.c leaves rmem_last, rmem_end, and rmem_owner stale after _msgpack_buffer_shift_chunk returns an rmem page to the shared pool, allowing a subsequent Buffer#write and a second MessagePack::Buffer to alias the page and disclose or corrupt cross-buffer data. This issue is fixed in version 1.8.2.
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
ruby-msgpack (PTS)	bullseye	1.1.0-2	vulnerable
	bookworm	1.4.2-2	vulnerable
	trixie	1.7.2-1.1	vulnerable
	forky	1.8.3-1	fixed
	sid	1.8.4-1	fixed

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

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
ruby-msgpack	source	(unstable)	1.8.3-1

Notes

https://github.com/msgpack/msgpack-ruby/security/advisories/GHSA-4mrv-5p47-p938
Fixed by: https://github.com/msgpack/msgpack-ruby/commit/5627d71606b565641d2dd501b82aae862f4abe90 (v1.8.2)