{"schema_version":"1.9.0","id":"CVE-2026-20796","published":"2026-02-13T10:30:03.445Z","modified":"2026-08-12T03:51:12.915106594Z","aliases":["GHSA-2xf7-hmf6-p64j","GO-2026-4495"],"related":["SUSE-SU-2026:0757-1","openSUSE-SU-2026:21483-1"],"summary":"Time-of-check time-of-use vulnerability in common teams API","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":[{"ranges":[{"type":"GIT","repo":"https://github.com/mattermost/mattermost","events":[{"introduced":"5b955468ea1ea8b56c0fb10feb258a36a767d7bb"},{"fixed":"ba27ba1f8cb1ffe2b1a79dc3d15a3ffa7de12fd7"}],"database_specific":{"cpe":"cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*","extracted_events":[{"introduced":"10.11.0"},{"fixed":"10.11.10"}],"source":"CPE_RANGE"}}],"versions":["v10.11.9","v10.11.9-rc1","v10.11.8","v10.11.7","v10.11.6","v10.11.5","v10.11.4-rc3","v10.11.4","v10.11.4-rc2","v10.11.4-rc1","v10.11.3","v10.11.2-rc2","v10.11.2","v10.11.2-rc1","v10.11.1","v10.11.1-rc1","v10.11.0-rc3","v10.11.0","mattermost-redux@10.11.0","@mattermost/types@10.11.0","@mattermost/client@10.11.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-20796.json"}}],"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/20xxx/CVE-2026-20796.json"},{"type":"ADVISORY","url":"https://mattermost.com/security-updates"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-20796"}],"database_specific":{"cna_assigner":"Mattermost","cwe_ids":["CWE-367"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/20xxx/CVE-2026-20796.json","unresolved_ranges":[{"extracted_events":[{"introduced":"10.11.0"},{"last_affected":"10.11.9"}],"source":"AFFECTED_FIELD"}]},"severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N"}]}