{"id":"CVE-2026-9859","aliases":["EUVD-2026-60541","GHSA-27x7-qjjm-4f83"],"status":"published","title":"Mattermost Boards plugin didn’t enforce role-based authorization on board channel link allowing board editors to expose boards to arbitrary channels","description":"Mattermost versions 11.7.x \u003c= 11.7.6, 10.11.x \u003c= 10.11.21, 11.8.x \u003c= 11.8.3 fail to enforce PermissionManageBoardRoles on the channelId field of the batch endpoint, which allows an authenticated board editor to relink any board they can edit to an arbitrary channel via a crafted PATCH request. Mattermost Advisory ID: MMSA-2026-00686","severity":{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-09","score":0.0034,"percentile":0.27725,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-863"],"published":"2026-08-17T22:06:26Z","modified":"2026-10-28T02:30:29Z","products":[{"vendor":"mattermost","product":"mattermost"},{"vendor":"mattermost","product":"mattermost_server"}],"references":[{"url":"https://mattermost.com/security-updates","tags":["vendor-advisory","Vendor Advisory","advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-9859","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-27x7-qjjm-4f83"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/9xxx/CVE-2026-9859.json","tags":["advisory"]}],"sources":{"cve":[{"id":"CVE-2026-9859","title":"Mattermost Boards plugin didn’t enforce role-based authorization on board channel link allowing board editors to expose boards to arbitrary channels","description":"Mattermost versions 11.7.x \u003c= 11.7.6, 10.11.x \u003c= 10.11.21, 11.8.x \u003c= 11.8.3 fail to enforce PermissionManageBoardRoles on the channelId field of the batch endpoint, which allows an authenticated board editor to relink any board they can edit to an arbitrary channel via a crafted PATCH request. Mattermost Advisory ID: MMSA-2026-00686","status":"published","published":"2026-08-17T22:06:26.318Z","modified":"2026-08-18T14:22:01.335Z","cvss":[{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N","level":"medium","assessor":"cna"}],"cwes":["CWE-863"],"updated_at":"2026-11-02T13:42:26.790871Z"}],"euvd":[{"id":"EUVD-2026-60541","description":"Mattermost versions 11.7.x \u003c= 11.7.6, 10.11.x \u003c= 10.11.21, 11.8.x \u003c= 11.8.3 fail to enforce PermissionManageBoardRoles on the channelId field of the batch endpoint, which allows an authenticated board editor to relink any board they can edit to an arbitrary channel via a crafted PATCH request. Mattermost Advisory ID: MMSA-2026-00686","status":"published","published":"2026-08-17T22:06:26Z","modified":"2026-08-18T14:22:01Z","cvss":[{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N","level":"medium"}],"updated_at":"2026-11-02T18:01:46.762528Z"}],"ghsa":[{"id":"GHSA-27x7-qjjm-4f83","title":"Mattermost versions 11.7.x \u003c= 11.7.6, 10.11.x \u003c= 10.11.21, 11.8.x \u003c= 11.8.3 fail to enforce...","description":"Mattermost versions 11.7.x \u003c= 11.7.6, 10.11.x \u003c= 10.11.21, 11.8.x \u003c= 11.8.3 fail to enforce PermissionManageBoardRoles on the channelId field of the batch endpoint, which allows an authenticated board editor to relink any board they can edit to an arbitrary channel via a crafted PATCH request. Mattermost Advisory ID: MMSA-2026-00686","status":"published","published":"2026-08-18T00:30:36Z","modified":"2026-08-18T00:30:43Z","cvss":[{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N","level":"medium"}],"cwes":["CWE-863"],"updated_at":"2026-11-02T15:10:35.792698Z"}],"nvd":[{"id":"CVE-2026-9859","description":"Mattermost versions 11.7.x \u003c= 11.7.6, 10.11.x \u003c= 10.11.21, 11.8.x \u003c= 11.8.3 fail to enforce PermissionManageBoardRoles on the channelId field of the batch endpoint, which allows an authenticated board editor to relink any board they can edit to an arbitrary channel via a crafted PATCH request. Mattermost Advisory ID: MMSA-2026-00686","status":"published","published":"2026-08-17T22:17:27.343Z","modified":"2026-08-19T13:28:57.893Z","cvss":[{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N","level":"medium","assessor":"secondary"}],"cwes":["CWE-863"],"updated_at":"2026-11-02T14:12:38.647684Z"}],"osv":[{"id":"CVE-2026-9859","title":"Mattermost Boards plugin didn’t enforce role-based authorization on board channel link allowing board editors to expose boards to arbitrary channels","description":"Mattermost versions 11.7.x \u003c= 11.7.6, 10.11.x \u003c= 10.11.21, 11.8.x \u003c= 11.8.3 fail to enforce PermissionManageBoardRoles on the channelId field of the batch endpoint, which allows an authenticated board editor to relink any board they can edit to an arbitrary channel via a crafted PATCH request. Mattermost Advisory ID: MMSA-2026-00686","status":"published","published":"2026-08-17T22:06:26.318Z","modified":"2026-10-28T02:30:29.554248542Z","cvss":[{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N","level":"medium"}],"cwes":["CWE-863"],"updated_at":"2026-11-02T15:45:21.933537Z"}]}}