Medium 5.4Published Jul 30, 2026

CVE-2026-54522MessagePack for Ruby is an implementation of the MessagePack binary serialization format.

Updated under an hour ago (2026-10-19 06:50 UTC)

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Exploited in the last 30 days

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.

CVSS: 5.4 MEDIUM (v3.1, NVD)CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
Weakness (CWE): CWE-416
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: Not given
NVD analysis: Analyzed
Record last updated: Aug 5, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

msgpack messagepack msgpack:messagepack	before 1.8.2	NVD

References

https://github.com/msgpack/msgpack-ruby/commit/5627d71606b565641d2dd501b82aae862f4abe90patch
https://github.com/msgpack/msgpack-ruby/security/advisories/GHSA-4mrv-5p47-p938exploit, vendor-advisory

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.