CVE-2026-54522

MessagePack::Buffer#clear Use-After-Free that Enables Cross-Buffer Disclosure

Published Jul 30, 2026 CVSS 4.0 · 2.1 Low EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-4mrv-5p47-p938 MessagePack::Buffer#clear Use-After-Free that Enables Cross-Buffer Disclosure
History
Type Values Removed Values Added
First Time appeared Msgpack
Msgpack msgpack
Vendors & Products Msgpack
Msgpack msgpack
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
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.
Title MessagePack::Buffer#clear Use-After-Free that Enables Cross-Buffer Disclosure
Weaknesses CWE-416
References
Metrics cvssV4_0

{'score': 2.1, 'vector': 'CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Jul 30, 2026, 5:39 PM
Reserved
Jun 15, 2026, 6:40 PM
Status
Analyzed
Published
Jul 30, 2026, 5:16 PM
Modified
Oct 23, 2026, 10:10 PM