{"id":"CVE-2026-16453","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-16453","generatedAt":"2026-10-28T06:35:58.703Z","title":"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…","description":"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","published":"2026-10-16T08:17:13.000Z","lastModified":"2026-10-16T19:23:19.000Z","status":"Awaiting Analysis","sourceIdentifier":"responsibledisclosure@mattermost.com","cvss":{"version":"3.1","score":7.1,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N"},"cwe":["CWE-472"],"affected":[],"epss":{"score":0.00186,"percentile":0.08155,"date":"2026-10-27","history":[{"date":"2026-10-16","score":0.00186,"percentile":0.07699}]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (0.19%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[{"kind":"new","label":"New CVE","at":"2026-10-16T08:17:13.000Z","detail":{"score":"7.1","severity":"HIGH","publishedAt":"2026-10-16T08:17:12.640Z"},"summary":"New CVE, high severity (CVSS 7.1)."}],"references":[{"url":"https://mattermost.com/security-updates","source":"responsibledisclosure@mattermost.com"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-16453","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}