{"schema_version":"1.9.0","id":"GHSA-xpvf-6qcc-9jqc","published":"2026-03-16T15:30:46Z","modified":"2026-03-23T18:56:04.837800Z","aliases":["CVE-2026-4265","GO-2026-4749"],"summary":"Mattermost fails to validate team-specific upload_file permissions","details":"Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to validate team-specific upload_file permissions which allows a guest user to post files in channels where they lack upload_file permission via uploading files in a team where they have permission and reusing the file metadata in a POST request to a different team. Mattermost Advisory ID: MMSA-2025-00553","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":"8.0.0-20260107144005-c7f6efdfb035"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/03/GHSA-xpvf-6qcc-9jqc/GHSA-xpvf-6qcc-9jqc.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":"5.3.2-0.20260107144005-c7f6efdfb035"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/03/GHSA-xpvf-6qcc-9jqc/GHSA-xpvf-6qcc-9jqc.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-rc1"},{"fixed":"10.11.11"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/03/GHSA-xpvf-6qcc-9jqc/GHSA-xpvf-6qcc-9jqc.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-rc1"},{"fixed":"11.2.3"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/03/GHSA-xpvf-6qcc-9jqc/GHSA-xpvf-6qcc-9jqc.json"}},{"package":{"name":"github.com/mattermost/mattermost-server","ecosystem":"Go","purl":"pkg:golang/github.com/mattermost/mattermost-server"},"ranges":[{"type":"SEMVER","events":[{"introduced":"11.3.0-rc1"},{"fixed":"11.3.1"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/03/GHSA-xpvf-6qcc-9jqc/GHSA-xpvf-6qcc-9jqc.json"}}],"references":[{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-4265"},{"type":"WEB","url":"https://github.com/mattermost/mattermost/commit/c7f6efdfb035490f494b3177996ee5f4b278c988"},{"type":"PACKAGE","url":"https://github.com/mattermost/mattermost"},{"type":"WEB","url":"https://mattermost.com/security-updates"}],"database_specific":{"cwe_ids":["CWE-863"],"github_reviewed":true,"github_reviewed_at":"2026-03-18T16:09:03Z","nvd_published_at":"2026-03-16T14:20:19Z","severity":"MODERATE"},"severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N"}]}