{"schema_version":"1.9.0","id":"GHSA-26wq-p25c-j6fv","published":"2026-10-08T17:40:01Z","modified":"2026-10-08T18:00:08.901031374Z","aliases":["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.","affected":[{"package":{"name":"msgpack5","ecosystem":"npm","purl":"pkg:npm/msgpack5"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"6.1.0"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-26wq-p25c-j6fv/GHSA-26wq-p25c-j6fv.json"}}],"references":[{"type":"WEB","url":"https://github.com/mcollina/msgpack5/security/advisories/GHSA-26wq-p25c-j6fv"},{"type":"WEB","url":"https://github.com/mcollina/msgpack5/commit/85da345bf1acc18ca441741e5cf4aa0ed0d69314"},{"type":"PACKAGE","url":"https://github.com/mcollina/msgpack5"},{"type":"WEB","url":"https://github.com/mcollina/msgpack5/releases/tag/v6.1.0"}],"database_specific":{"cwe_ids":["CWE-228"],"github_reviewed":true,"github_reviewed_at":"2026-10-08T17:40:01Z","nvd_published_at":null,"severity":"MODERATE"},"severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H"}]}