CVE-2026-54522 — Security Box Score

CVE · referencelatest edition

Reference page — cumulative record through Wednesday, August 19, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2026-54522LOW

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

  AV  AC  AT  PR  UI  VC  VI  VA   CVSS    EPSS   %ile   KEV
   L   L   P   N   N   L   N   N    2.1   .0014    3.5     —

AFFECTED
  Product       Versions   Fixed
  msgpack-ruby  < 1.8.2 –  —

TIMELINE
  Jun 15  Reserved by GitHub_M
  Jul 30  EXPLOIT PUBLISHED — CVE-2026-54522 (msgpack-ruby). Public exploit reference added.
  Jul 30  Published (CNA: GitHub_M)

CWE-416 · CNA: GitHub_M · CVSS v4.0 · 2 references · NVD status: Analyzed

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.

Lifecycle

Complete event history — 3 events, chronological
Date	Event	Detail
June 15, 2026	Reserved	Reserved by GitHub_M
July 30, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2026-54522 (msgpack-ruby). Public exploit reference added.
July 30, 2026	Published	Published (CNA: GitHub_M)

Affected

Affected products and packages — 1 row
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
msgpack	msgpack-ruby	—	< 1.8.2	—

Weaknesses

CWE-416

References (2)

https://github.com/msgpack/msgpack-ruby/commit/5627d71606b565641d2dd501b82aae862f4abe90 [Patch]
https://github.com/msgpack/msgpack-ruby/security/advisories/GHSA-4mrv-5p47-p938 [Exploit, Vendor Advisory]

Authoritative record: CVE-2026-54522 at cve.org

Vendors: msgpack

Weaknesses: CWE-416

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-54522 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Wednesday, August 19, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.