CVE-2026-54522CWE-416

CVE-2026-54522

Medium · published July 30, 2026

CVSS v3.1

5.4

EPSS

Percentile

12.7

In the wild

Unconfirmed

What it is

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.

The record

Technical detail

CVSS v3.1: 5.4 · MEDIUM
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
CVSS v4.0: Not supplied
EPSS: 0.00227 · 12.7th percentile
Weakness: CWE-416 · Use After Free
Published: 2026-07-30T21:16Z

Affected products (1)

Product	Versions	Fixed in
msgpack/messagepack	< 1.8.2	1.8.2

References (3)

https://github.com/msgpack/msgpack-ruby/commit/5627d71606b565641d2dd501b82aae862f4abe90 · [email protected]https://github.com/msgpack/msgpack-ruby/security/advisories/GHSA-4mrv-5p47-p938 · [email protected]https://github.com/msgpack/msgpack-ruby/security/advisories/GHSA-4mrv-5p47-p938 · 134c704f-9b21-4f2e-91b3-4a467353bcc0

EPSS history

Timeline

30 JUL 16:33Z
MessagePack::Buffer#clear Use-After-Free that Enables Cross-Buffer Disclosure
cvelistv5