VulnerabilityAnalyzed

CVE-2026-54522

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…

LOW 2.1EPSS 0.16%

Does this matter?

Lower severity and a low EPSS score (0.16%). Track it; it rarely justifies an emergency change on its own.

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.

CVSS 4.0: 2.1 LOWCVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/M
EPSS: 0.16% probability · 6th percentile
CISA KEV: Not listed
Weakness: CWE-416
Affected: msgpack/messagepack
Source: security-advisories@github.com

References

https://github.com/msgpack/msgpack-ruby/commit/5627d71606b565641d2dd501b82aae862f4abe90Patch
https://github.com/msgpack/msgpack-ruby/security/advisories/GHSA-4mrv-5p47-p938Exploit, Vendor Advisory
https://github.com/msgpack/msgpack-ruby/security/advisories/GHSA-4mrv-5p47-p938Exploit, Vendor Advisory

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.