{"schema_version":"1.3.1","id":"GO-2026-5838","modified":"2026-07-07T15:26:32Z","published":"2026-07-07T15:26:32Z","aliases":["CVE-2026-5740","GHSA-w9m8-p4cc-4qj9"],"summary":"Mattermost doesn't properly validate msgpack-encoded WebSocket frames before memory allocation in github.com/mattermost/mattermost-server","details":"Mattermost doesn't properly validate msgpack-encoded WebSocket frames before memory allocation in github.com/mattermost/mattermost-server","affected":[{"package":{"name":"github.com/mattermost/mattermost-server","ecosystem":"Go"},"ranges":[{"type":"SEMVER","events":[{"introduced":"10.11.0+incompatible"},{"fixed":"10.11.15+incompatible"},{"introduced":"11.4.0+incompatible"},{"fixed":"11.4.5+incompatible"},{"introduced":"11.5.0+incompatible"},{"fixed":"11.5.4+incompatible"},{"introduced":"11.6.0+incompatible"},{"fixed":"11.6.1+incompatible"}]}],"ecosystem_specific":{}},{"package":{"name":"github.com/mattermost/mattermost-server/v5","ecosystem":"Go"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"}]}],"ecosystem_specific":{}},{"package":{"name":"github.com/mattermost/mattermost-server/v6","ecosystem":"Go"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"}]}],"ecosystem_specific":{}},{"package":{"name":"github.com/mattermost/mattermost/server/v8","ecosystem":"Go"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"8.0.0-20260410202636-17939826efa2"}]}],"ecosystem_specific":{}}],"references":[{"type":"ADVISORY","url":"https://github.com/advisories/GHSA-w9m8-p4cc-4qj9"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-5740"},{"type":"WEB","url":"https://github.com/mattermost/mattermost/commit/17939826efa20a97f087b3d390ec5136df350bae"},{"type":"WEB","url":"https://mattermost.com/security-updates"}],"database_specific":{"url":"https://pkg.go.dev/vuln/GO-2026-5838","review_status":"UNREVIEWED"}}