{"id":"CVE-2026-12985","summary":"Mattermost DCR redirect URI allowlist bypass via improper URL component validation","details":"Mattermost versions 11.9.x \u003c= 11.9.0, 11.8.x \u003c= 11.8.4, 11.7.x \u003c= 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","modified":"2026-10-09T02:49:21.859670790Z","published":"2026-09-14T14:09:53.799Z","database_specific":{"cwe_ids":["CWE-601"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/12xxx/CVE-2026-12985.json","unresolved_ranges":[{"extracted_events":[{"introduced":"11.8.0"},{"last_affected":"11.8.4"},{"introduced":"11.7.0"},{"last_affected":"11.7.7"},{"introduced":"11.9.0"},{"last_affected":"11.9.0"}],"source":"AFFECTED_FIELD"}],"cna_assigner":"Mattermost"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/12xxx/CVE-2026-12985.json"},{"type":"ADVISORY","url":"https://mattermost.com/security-updates"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-12985"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/mattermost/mattermost","events":[{"introduced":"a9e574a82633915f22071f0d7ca2b006f249ec2a"},{"fixed":"d42004bb3046de3ed176938a34b1a70c1c3d9421"},{"introduced":"e8bd2b8a871cbeff6943bead62328478118188df"},{"fixed":"d9c17e42b19c27dfac0ebe6840d954a41e626890"},{"introduced":"583461af10fc9b2aef2871c722fc4376db695832"},{"fixed":"1f738d345805168964a55e5860aac9c747dceb78"}],"database_specific":{"extracted_events":[{"introduced":"11.7.0"},{"fixed":"11.7.8"},{"introduced":"11.8.0"},{"fixed":"11.8.5"},{"introduced":"11.9.0"},{"fixed":"11.9.1"}],"source":"CPE_RANGE","cpe":"cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*"}}],"versions":["v11.8.4","v11.7.7","v11.9.0","mattermost-redux@11.9.0","@mattermost/types@11.9.0","@mattermost/shared@11.9.0","@mattermost/client@11.9.0","v11.8.3","v11.7.6","v11.8.2","v11.7.5-rc1","v11.7.5","v11.8.1","v11.7.4","v11.7.3","v11.8.0-rc5","v11.8.0","mattermost-redux@11.8.0","@mattermost/types@11.8.0","@mattermost/shared@11.8.0","@mattermost/client@11.8.0","v11.7.2","v11.7.1","v11.7.0","mattermost-redux@11.7.0","@mattermost/types@11.7.0","@mattermost/shared@11.7.0","@mattermost/client@11.7.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-12985.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N"}]}