{"id":"CVE-2026-16047","aliases":["EUVD-2026-60208","GHSA-7xj3-8pxr-p8pc"],"status":"published","title":"Board channel linking without read channel permission validation","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 validate that users have read access to a channel before linking a board to it, which allows an authenticated attacker to discover the membership of private channels on the same team via creating, patching, importing, or bulk-creating boards with an arbitrary channelId. Mattermost Advisory ID: MMSA-2026-00674","severity":{"version":"3.1","score":4.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-09","score":0.0027,"percentile":0.19345,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-862"],"published":"2026-08-17T14:25:08Z","modified":"2026-10-28T02:31:14Z","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-2026-16047","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-7xj3-8pxr-p8pc"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/16xxx/CVE-2026-16047.json","tags":["advisory"]}],"sources":{"cve":[{"id":"CVE-2026-16047","title":"Board channel linking without read channel permission validation","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 validate that users have read access to a channel before linking a board to it, which allows an authenticated attacker to discover the membership of private channels on the same team via creating, patching, importing, or bulk-creating boards with an arbitrary channelId. Mattermost Advisory ID: MMSA-2026-00674","status":"published","published":"2026-08-17T14:25:08.338Z","modified":"2026-08-17T15:26:34.376Z","cvss":[{"version":"3.1","score":4.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N","level":"medium","assessor":"cna"}],"cwes":["CWE-862"],"updated_at":"2026-11-02T14:20:10.870108Z"}],"euvd":[{"id":"EUVD-2026-60208","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 validate that users have read access to a channel before linking a board to it, which allows an authenticated attacker to discover the membership of private channels on the same team via creating, patching, importing, or bulk-creating boards with an arbitrary channelId. Mattermost Advisory ID: MMSA-2026-00674","status":"published","published":"2026-08-17T14:25:08Z","modified":"2026-08-17T15:26:34Z","cvss":[{"version":"3.1","score":4.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N","level":"medium"}],"updated_at":"2026-11-02T18:01:49.335011Z"}],"ghsa":[{"id":"GHSA-7xj3-8pxr-p8pc","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 validate that...","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 validate that users have read access to a channel before linking a board to it, which allows an authenticated attacker to discover the membership of private channels on the same team via creating, patching, importing, or bulk-creating boards with an arbitrary channelId. Mattermost Advisory ID: MMSA-2026-00674","status":"published","published":"2026-08-17T15:30:40Z","modified":"2026-08-17T15:30:41Z","cvss":[{"version":"3.1","score":4.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N","level":"medium"}],"cwes":["CWE-862"],"updated_at":"2026-11-02T15:10:34.652326Z"}],"nvd":[{"id":"CVE-2026-16047","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 validate that users have read access to a channel before linking a board to it, which allows an authenticated attacker to discover the membership of private channels on the same team via creating, patching, importing, or bulk-creating boards with an arbitrary channelId. Mattermost Advisory ID: MMSA-2026-00674","status":"published","published":"2026-08-17T15:16:54.193Z","modified":"2026-08-18T20:41:36.52Z","cvss":[{"version":"3.1","score":4.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N","level":"medium","assessor":"secondary"}],"cwes":["CWE-862"],"updated_at":"2026-11-02T14:12:38.647684Z"}],"osv":[{"id":"CVE-2026-16047","title":"Board channel linking without read channel permission validation","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 validate that users have read access to a channel before linking a board to it, which allows an authenticated attacker to discover the membership of private channels on the same team via creating, patching, importing, or bulk-creating boards with an arbitrary channelId. Mattermost Advisory ID: MMSA-2026-00674","status":"published","published":"2026-08-17T14:25:08.338Z","modified":"2026-10-28T02:31:14.108041302Z","cvss":[{"version":"3.1","score":4.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N","level":"medium"}],"cwes":["CWE-862"],"updated_at":"2026-11-02T15:44:57.682091Z"}]}}