{"id":"CVE-2026-28759","revision":"3f005fd7595e4777bac5f0b393e443bd","records":[{"revision":"3f005fd7595e4777bac5f0b393e443bd","observedAt":"2026-10-25T07:19:03.231+00:00","statement":{"source":"nvd","id":"CVE-2026-28759","aliases":[],"title":"Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 fail to validate that a remote cluster has access to a channel before processing membership removal requests during shared channel membership sync, which allows a m…","description":"Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 fail to validate that a remote cluster has access to a channel before processing membership removal requests during shared channel membership sync, which allows a malicious remote cluster to remove any user from any channel, including private channels, via crafted membership sync messages targeting channels the remote cluster is not authorized to access. Mattermost Advisory ID: MMSA-2026-00576","state":0,"publishedAt":"2026-05-18T08:16:13.573+00:00","modifiedAt":"2026-10-14T20:10:00.19+00:00","affected":[],"metrics":[{"system":"CVSS 3.1 · responsibledisclosure@mattermost.com · Secondary","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N","score":4.3,"severity":"MEDIUM"}],"references":["https://mattermost.com/security-updates"],"sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-28759","license":"NIST NVD usage terms; underlying source attribution retained","enrichment":{"sourceStatus":"Analyzed","weaknesses":["CWE-863"],"productCriteria":["cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*"],"sourceDates":{"published":"2026-05-18T08:16:13.573","lastModified":"2026-10-14T20:10:00.190"},"relatedAdvisories":[],"note":"NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON."},"key":"nvd:CVE-2026-28759","identifiers":["CVE-2026-28759"]},"retained":false,"historicalAffected":[]}],"coverage":[]}