{"id":"CVE-2026-63097","state":"PUBLISHED","title":"Dendrite 0.13.8 syncapi /context Endpoint Post-Leave State Exposure","description":"Dendrite through 0.13.8 contains an improper access control vulnerability in the syncapi /context endpoint (syncapi/routing/context.go) that allows authenticated local users to access post-leave room state events by exploiting a flawed membership check that evaluates only the RoomExists field while ignoring IsInRoom, HasBeenInRoom, and Membership fields. Attackers who have left a room can call the rooms context API endpoint for a previously permitted event and receive unfiltered current room state that the /messages and /sync endpoints correctly withhold.","publishedAt":"2026-07-17T15:32:45.411Z","updatedAt":"2026-07-28T01:50:00.775Z","severity":{"score":5.3,"label":"Medium","version":"4.0","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N","source":"VulnCheck"},"assigner":"VulnCheck","products":["matrix-org dendrite"],"affected":[{"vendor":"matrix-org","product":"dendrite","defaultStatus":"affected","versions":[{"version":"0","status":"affected","lessThanOrEqual":"0.13.8","versionType":"semver"}],"repo":"https://github.com/matrix-org/dendrite"}],"references":["https://github.com/geo-chen/oss/blob/main/dendrite.md#finding-3-context-returns-current-room-state-to-non-members-and-left-users-history-visibility-bypass","https://www.vulncheck.com/advisories/dendrite-syncapi-context-endpoint-post-leave-state-exposure"],"weaknesses":["CWE-863"],"ingestedAt":"2026-10-29T20:12:41.951Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/63xxx/CVE-2026-63097.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-63097","state":"PUBLISHED","datePublished":"2026-07-17T15:32:45.411Z","dateUpdated":"2026-07-28T01:50:00.775Z","assignerShortName":"VulnCheck","assignerOrgId":"83251b91-4cc7-4094-a5c7-464a1b83ea10","dateReserved":"2026-07-15T15:45:44.601Z"},"containers":{"cna":{"title":"Dendrite 0.13.8 syncapi /context Endpoint Post-Leave State Exposure","descriptions":[{"lang":"en","value":"Dendrite through 0.13.8 contains an improper access control vulnerability in the syncapi /context endpoint (syncapi/routing/context.go) that allows authenticated local users to access post-leave room state events by exploiting a flawed membership check that evaluates only the RoomExists field while ignoring IsInRoom, HasBeenInRoom, and Membership fields. 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