{"id":"CVE-2026-15754","summary":"Missing per-channel team-scope check in ABAC access control policy unassign allows cross-team policy removal","details":"Mattermost versions 11.7.x \u003c= 11.7.6, 11.8.x \u003c= 11.8.3 The access control policy unassign endpoint fails to re-validate that each target channel still belongs to the requesting admin's team, which allows an authenticated team administrator to remove ABAC (attribute-based access control) policy assignments from channels outside their team via the policy unassign API after a channel has been moved to another team.. Mattermost Advisory ID: MMSA-2026-00718","modified":"2026-08-20T03:54:12.190335850Z","published":"2026-08-17T14:36:56.282Z","database_specific":{"unresolved_ranges":[{"source":"AFFECTED_FIELD","extracted_events":[{"introduced":"11.7.0"},{"last_affected":"11.7.6"},{"introduced":"11.8.0"},{"last_affected":"11.8.3"}]}],"cna_assigner":"Mattermost","cwe_ids":["CWE-863"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/15xxx/CVE-2026-15754.json"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/15xxx/CVE-2026-15754.json"},{"type":"ADVISORY","url":"https://mattermost.com/security-updates"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-15754"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/mattermost/mattermost","events":[{"introduced":"a9e574a82633915f22071f0d7ca2b006f249ec2a"},{"fixed":"2045acd92c40353abfc5ffff8ae1e0dd9d2e6737"},{"introduced":"e8bd2b8a871cbeff6943bead62328478118188df"},{"fixed":"92d79e4d0cda808c3f63217a62d068472c184099"}],"database_specific":{"extracted_events":[{"introduced":"11.7.0"},{"fixed":"11.7.7"},{"introduced":"11.8.0"},{"fixed":"11.8.4"}],"source":"CPE_RANGE","cpe":"cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*"}}],"versions":["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-2026-15754.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:N/I:H/A:N"}]}