{"action":"Upgrade github.com/mattermost/mattermost/server/v8 to 8.0.0-20260216150504-8738f8c4b3d4 or later.","affected":[{"fixed":"11.5.2","introduced":"11.5.0"},{"fixed":"10.11.14","introduced":"10.11.0"},{"fixed":"11.4.4","introduced":"11.4.0"},{"fixed":"8.0.0-20260216150504-8738f8c4b3d4","introduced":"0"}],"component":"github.com/mattermost/mattermost/server/v8","cve_ids":["CVE-2026-28759"],"ecosystem":"Go","epss":0.00152,"exploited":false,"fixed_versions":["11.5.2","10.11.14","11.4.4","8.0.0-20260216150504-8738f8c4b3d4"],"ghsa_id":"GHSA-8h9w-w78c-vvr3","id":"tcs_01M5KF3T8V4HZ74BF07ARRNYRB","modified_at":"2026-06-25T19:56:34.145333656Z","published_at":"2026-05-18T09:31:47Z","references":["https://osv.dev/vulnerability/GHSA-8h9w-w78c-vvr3","https://nvd.nist.gov/vuln/detail/CVE-2026-28759","https://github.com/mattermost/mattermost/commit/8738f8c4b3d42b2b687a6231e72f313357a2e891","https://github.com/mattermost/mattermost","https://mattermost.com/security-updates"],"severity":{"label":"medium","score":4.3},"sources":[{"source":"osv","source_id":"GHSA-8h9w-w78c-vvr3","url":"https://osv.dev/vulnerability/GHSA-8h9w-w78c-vvr3"}],"summary":"Mattermost does not verify remote cluster channel access when processing shared channel membership removals"}