{"schema_version":"1.7.3","id":"GHSA-2xf7-hmf6-p64j","published":"2026-02-13T12:31:21Z","modified":"2026-02-23T19:41:17.607287Z","aliases":["CVE-2026-20796","GO-2026-4495"],"summary":"Mattermost doesn't properly validate channel membership at the time of data retrieval","details":"Mattermost versions 10.11.x <= 10.11.9 fail to properly validate channel membership at the time of data retrieval which allows a deactivated user to learn team names they should not have access to via a race condition in the /common_teams API endpoint.. Mattermost Advisory ID: MMSA-2025-00549","affected":[{"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"},{"fixed":"10.11.10"}]}],"database_specific":{"last_known_affected_version_range":"<= 10.11.9","source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/02/GHSA-2xf7-hmf6-p64j/GHSA-2xf7-hmf6-p64j.json"}}],"references":[{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-20796"},{"type":"PACKAGE","url":"https://github.com/mattermost/mattermost"},{"type":"WEB","url":"https://mattermost.com/security-updates"}],"database_specific":{"cwe_ids":["CWE-367"],"github_reviewed":true,"github_reviewed_at":"2026-02-13T20:55:54Z","nvd_published_at":"2026-02-13T11:16:10Z","severity":"LOW"},"severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N"}]}