{"schema_version":"1.7.5","id":"GHSA-3c9r-7f29-qp32","published":"2026-02-16T12:30:24Z","modified":"2026-04-01T17:34:48.742132Z","aliases":["CVE-2026-0999","GO-2026-4520"],"summary":"Mattermost fails to properly validate login method restrictions","details":"Mattermost versions 11.1.x <= 11.1.2, 10.11.x <= 10.11.9, 11.2.x <= 11.2.1 fail to properly validate login method restrictions which allows an authenticated user to bypass SSO-only login requirements via userID-based authentication. Mattermost Advisory ID: MMSA-2025-00548","affected":[{"package":{"name":"github.com/mattermost/mattermost/server/v8","ecosystem":"Go","purl":"pkg:golang/github.com/mattermost/mattermost/server/v8"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"8.0.0-20251212052346-61651b0df7ea"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/02/GHSA-3c9r-7f29-qp32/GHSA-3c9r-7f29-qp32.json"}},{"package":{"name":"github.com/mattermost/mattermost-server","ecosystem":"Go","purl":"pkg:golang/github.com/mattermost/mattermost-server"},"ranges":[{"type":"SEMVER","events":[{"introduced":"11.1.0"}]}],"database_specific":{"last_known_affected_version_range":"< 11.1.3","source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/02/GHSA-3c9r-7f29-qp32/GHSA-3c9r-7f29-qp32.json"}},{"package":{"name":"github.com/mattermost/mattermost-server","ecosystem":"Go","purl":"pkg:golang/github.com/mattermost/mattermost-server"},"ranges":[{"type":"SEMVER","events":[{"introduced":"10.11.0"}]}],"database_specific":{"last_known_affected_version_range":"< 10.11.10","source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/02/GHSA-3c9r-7f29-qp32/GHSA-3c9r-7f29-qp32.json"}},{"package":{"name":"github.com/mattermost/mattermost-server","ecosystem":"Go","purl":"pkg:golang/github.com/mattermost/mattermost-server"},"ranges":[{"type":"SEMVER","events":[{"introduced":"11.2.0"}]}],"database_specific":{"last_known_affected_version_range":"< 11.2.2","source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/02/GHSA-3c9r-7f29-qp32/GHSA-3c9r-7f29-qp32.json"}},{"package":{"name":"github.com/mattermost/mattermost-server","ecosystem":"Go","purl":"pkg:golang/github.com/mattermost/mattermost-server"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"5.3.2-0.20251212052346-61651b0df7ea"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/02/GHSA-3c9r-7f29-qp32/GHSA-3c9r-7f29-qp32.json"}}],"references":[{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-0999"},{"type":"WEB","url":"https://github.com/mattermost/mattermost/commit/61651b0df7ea5db55d1e54f8d6fb5fce4149309c"},{"type":"PACKAGE","url":"https://github.com/mattermost/mattermost"},{"type":"WEB","url":"https://mattermost.com/security-updates"}],"database_specific":{"cwe_ids":["CWE-303"],"github_reviewed":true,"github_reviewed_at":"2026-02-19T19:34:56Z","nvd_published_at":"2026-02-16T10:16:08Z","severity":"MODERATE"},"severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N"}]}