{"id":"CVE-2026-54522","aliases":["GHSA-4mrv-5p47-p938"],"url":"https://o3.security/vulnerability/CVE-2026-54522","summary":"MessagePack::Buffer#clear Use-After-Free that Enables Cross-Buffer Disclosure","details":"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.","published":"2026-07-30T16:33:06.080Z","modified":"2026-08-12T16:41:18.513154Z","cvss":null,"epss":{"score":0.00164,"percentile":0.05956,"asOf":"2026-09-14"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"RubyGems","name":"msgpack","fixedVersion":"1.8.2"}],"fix":{"url":"https://github.com/msgpack/msgpack-ruby/commit/5627d71606b565641d2dd501b82aae862f4abe90","label":"msgpack/msgpack-ruby@5627d71"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/54xxx/CVE-2026-54522.json"},{"type":"ADVISORY","url":"https://github.com/msgpack/msgpack-ruby/security/advisories/GHSA-4mrv-5p47-p938"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-54522"},{"type":"FIX","url":"https://github.com/msgpack/msgpack-ruby/commit/5627d71606b565641d2dd501b82aae862f4abe90"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T16:41:18.513154Z"}}