{"id":"CVE-2026-107299","aliases":["GHSA-26wq-p25c-j6fv"],"url":"https://o3.security/vulnerability/CVE-2026-107299","summary":"msgpack5: Reserved byte can cause unbounded stream buffering","details":"### Impact\n\nThe reserved MessagePack byte `0xc1` is incorrectly treated as incomplete input. When it appears at the start of a decoder stream, all subsequent data is retained while the decoder waits for bytes that can never make the value valid, allowing memory exhaustion.\n\n### Patches\n\nThe decoder now rejects `0xc1` as invalid input. Streaming decoders release buffered input and stop after unrecoverable decoding errors.\n\n### Workarounds\n\nReject `0xc1` before streaming input to msgpack5, and enforce stream byte and time limits.","published":"2026-10-08T17:09:47.191Z","modified":"2026-10-21T02:54:36.404831335Z","cvss":{"score":5.9,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"npm","name":"msgpack5","fixedVersion":"6.1.0"}],"fix":{"url":"https://github.com/mcollina/msgpack5/commit/85da345bf1acc18ca441741e5cf4aa0ed0d69314","label":"mcollina/msgpack5@85da345"},"references":[{"type":"WEB","url":"https://github.com/mcollina/msgpack5/releases/tag/v6.1.0"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/107xxx/CVE-2026-107299.json"},{"type":"ADVISORY","url":"https://github.com/mcollina/msgpack5/security/advisories/GHSA-26wq-p25c-j6fv"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-107299"},{"type":"FIX","url":"https://github.com/mcollina/msgpack5/commit/85da345bf1acc18ca441741e5cf4aa0ed0d69314"},{"type":"PACKAGE","url":"https://github.com/mcollina/msgpack5"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-21T02:54:36.404831335Z"}}