CVE-2026-54522

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.

Score

CVSS 3.1 5.4 Medium

Status

Analyzed - security-advisories@github.com

Published

2026-07-30

Last modified

2026-10-23

Weaknesses

CWE-416

Affected products

• Messagepack (Msgpack)
• Msgpack-ruby (Msgpack)

References

• https://github.com/msgpack/msgpack-ruby/security/advisories/GHSA-4mrv-5p47-p938
• https://github.com/msgpack/msgpack-ruby/commit/5627d71606b565641d2dd501b82aae862f4abe90