{"schema":"threatline.record/2","record":{"id":"CVE-2026-16453","aliases":[],"summary":"Mattermost SAML RelayState forgery allows unauthorized team membership","details":"Mattermost versions 11.10.x <= 11.10.0, 11.7.x <= 11.7.9, 11.9.x <= 11.9.1, 11.8.x <= 11.8.5 fail to verify the integrity of the SAML RelayState POST parameter which allows an authenticated SAML user to join any team, including invite-only teams, via forging the team_id or invite_id fields in the RelayState.. Mattermost Advisory ID: MMSA-2026-00727","categories":["Applications & CMS"],"product":"Mattermost","vendor":"Mattermost","ecosystem":null,"affected_ranges":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-16453","source_modified_at":"2026-10-16T14:18:12.181Z","fetched_at":"2026-10-23T18:48:36.087640Z","product":"Mattermost","vendor":"Mattermost","versions":[{"lessThanOrEqual":"11.10.0","status":"affected","version":"11.10.0","versionType":"semver"},{"lessThanOrEqual":"11.7.9","status":"affected","version":"11.7.0","versionType":"semver"},{"lessThanOrEqual":"11.9.1","status":"affected","version":"11.9.0","versionType":"semver"},{"lessThanOrEqual":"11.8.5","status":"affected","version":"11.8.0","versionType":"semver"},{"version":"11.11.0","status":"unaffected"},{"version":"11.10.1","status":"unaffected"},{"version":"11.7.10","status":"unaffected"},{"version":"11.9.2","status":"unaffected"},{"version":"11.8.6","status":"unaffected"}],"defaultStatus":"unaffected"}],"fixed_versions":[],"cvss":7.1,"severity":"High","kev":{"listed":false},"epss":{"probability":0.00186,"percentile":0.07823,"score_date":"2026-10-23"},"published_at":"2026-10-16T07:08:48.627Z","modified_at":"2026-10-16T14:18:12.181Z","provenance":[{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-16453","fetched_at":"2026-10-23T18:48:36.087640Z","source_modified_at":"2026-10-16T14:18:12.181Z"},{"source":"EPSS","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-16453","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-23"}],"sources":["CVE List","EPSS"],"references":[{"source":"CVE List","url":"https://mattermost.com/security-updates","tags":["vendor-advisory"]}],"locations":[],"motoko_assessment":{"status":"requires_architecture_review","automatic_remediation":false},"cve_state":"PUBLISHED","cvss_source":"CVE List","ssvc":{"exploitation":"none","automatable":"no","technical_impact":"partial","assessed_at":"2026-10-16T14:17:45.764516Z"},"classification":{"method":"product-first software-layer rules","rules_version":"2.1","matched_on":"product","confidence":"heuristic","reviewed":false},"change_timestamp":"2026-10-16T14:18:12.181Z","content_hash":"348271c9c9528ef0427ed344d3ba179daac4c3dbb0ec3f447336c9a934e3414d"}}