CVE-2026-54522MessagePack::Buffer#clear Use-After-Free that Enables Cross-Buffer Disclosure
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No exploitation reported and no EPSS estimate yet.
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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
- 2.1 LOW (v4.0, CNA)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
- 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
- GitHub_M
- NVD analysis
- Analyzed
- Record last updated
- Jul 30, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
msgpack msgpack-ruby msgpack:ruby (from the name) | before 1.8.2 | CNA record |
msgpack messagepack msgpack:messagepack | before 1.8.2 | NVD |
References
- https://github.com/msgpack/msgpack-ruby/security/advisories/GHSA-4mrv-5p47-p938x-refsource-confirm, exploit, vendor-advisory
- https://github.com/msgpack/msgpack-ruby/commit/5627d71606b565641d2dd501b82aae862f4abe90x-refsource-misc, patch
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.