{"id":"CVE-2026-12985","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-12985","generatedAt":"2026-10-28T01:42:24.533Z","title":"Mattermost versions 11.9.x <= 11.9.0, 11.8.x <= 11.8.4, 11.7.x <= 11.7.7 Mattermost failed to validate Dynamic Client Registration redirect URIs by URL component (matching glob patterns against the raw URI string instead) which allows a remote…","description":"Mattermost versions 11.9.x <= 11.9.0, 11.8.x <= 11.8.4, 11.7.x <= 11.7.7 Mattermost failed to validate Dynamic Client Registration redirect URIs by URL component (matching glob patterns against the raw URI string instead) which allows a remote unauthenticated attacker to register an OAuth client with an attacker-controlled callback host that bypasses the configured redirect URI allowlist via a crafted redirect URI that places an allowlisted host/path suffix inside the query string.. Mattermost Advisory ID: MMSA-2026-00700","published":"2026-09-14T15:17:04.000Z","lastModified":"2026-10-07T17:58:56.000Z","status":"Analyzed","sourceIdentifier":"responsibledisclosure@mattermost.com","cvss":{"version":"3.1","score":9.3,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N"},"cwe":["CWE-601"],"affected":["mattermost/mattermost server"],"epss":{"score":0.00268,"percentile":0.18739,"date":"2026-10-26","history":[]},"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 (0.27%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[{"kind":"scored","label":"Newly scored","at":"2026-10-07T18:00:08.000Z","detail":{"from":"6.8","score":"9.3","severity":"CRITICAL","fromSeverity":"MEDIUM"},"summary":"Now scored CVSS 9.3 CRITICAL (was 6.8)."}],"references":[{"url":"https://mattermost.com/security-updates","tags":["Vendor Advisory"],"source":"responsibledisclosure@mattermost.com"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-12985","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."}