{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-16453","assignerOrgId":"9302f53e-dde5-4bf3-b2f2-a83f91ac0eee","state":"PUBLISHED","assignerShortName":"Mattermost","dateReserved":"2026-07-21T10:00:44.943Z","datePublished":"2026-10-16T07:08:48.627Z","dateUpdated":"2026-10-16T14:18:12.181Z"},"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","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"}]}],"credits":[{"lang":"en","type":"finder","value":"Doyensec"}],"descriptions":[{"lang":"en","value":"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"}],"metrics":[{"cvssV3_1":{"attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"LOW","availabilityImpact":"NONE","version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N","baseSeverity":"HIGH","baseScore":7.1},"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}]}],"problemTypes":[{"descriptions":[{"lang":"en","type":"CWE","description":"CWE-472: External Control of Assumed-Immutable Web Parameter","cweId":"CWE-472"}]}],"references":[{"url":"https://mattermost.com/security-updates","name":"MMSA-2026-00727","tags":["vendor-advisory"]}],"solutions":[{"value":"Update Mattermost to versions 11.11.0, 11.10.1, 11.7.10, 11.9.2, 11.8.6 or higher.","lang":"en"}],"source":{"advisory":"MMSA-2026-00727","defect":["https://mattermost.atlassian.net/browse/MM-69888"],"discovery":"EXTERNAL"},"title":"Mattermost SAML RelayState forgery allows unauthorized team membership","providerMetadata":{"orgId":"9302f53e-dde5-4bf3-b2f2-a83f91ac0eee","shortName":"Mattermost","dateUpdated":"2026-10-16T07:08:48.627Z"},"x_generator":{"engine":"cvelib 1.8.0"}},"adp":[{"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-10-16T14:17:45.764516Z","id":"CVE-2026-16453","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"title":"CISA ADP Vulnrichment","providerMetadata":{"orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","shortName":"CISA-ADP","dateUpdated":"2026-10-16T14:18:12.181Z"}}]}}