CVE-2026-54522

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.

At a glance

Exploitability

Can be exploited locally on the machine without logging in. Limited direct impact.

Exploit odds

0.2% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-07-30 17:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-10-23 22:10 UTC Last updatedMost recent change to the record

Details

Published

2026-07-30 17:16 UTC

Last modified

2026-10-23 22:10 UTC

Exploit probability

0.2% · EPSS, next 30 days

Weakness

CWE-416 · Use after free

Record status

Analyzed

Affected

• Msgpack Messagepack < 1.8.2

Attack profile CVSS 4.0 · 2.1

Attack vector

Local

Complexity

Low

Attack requirements

Present

Privileges needed

None

User interaction

None

Confidentiality

Low

Integrity

None

Availability

None