{"action":"Upgrade github.com/mattermost/mattermost-server to 10.11.14+incompatible or later.","affected":[{"fixed":"10.11.14+incompatible","introduced":"10.11.0+incompatible"},{"fixed":"11.4.4+incompatible","introduced":"11.4.0+incompatible"},{"fixed":"11.5.2+incompatible","introduced":"11.5.0+incompatible"}],"component":"github.com/mattermost/mattermost-server","cve_ids":["CVE-2026-28759"],"ecosystem":"Go","epss":0.00152,"exploited":false,"fixed_versions":["10.11.14+incompatible","11.4.4+incompatible","11.5.2+incompatible"],"ghsa_id":"GHSA-8h9w-w78c-vvr3","id":"tcs_01M5KGK0X5XNNEDG27QM5NSRQT","modified_at":"2026-06-25T19:45:26.220689565Z","published_at":"2026-06-25T18:43:15Z","references":["https://osv.dev/vulnerability/GO-2026-5256","https://github.com/advisories/GHSA-8h9w-w78c-vvr3","https://nvd.nist.gov/vuln/detail/CVE-2026-28759","https://github.com/mattermost/mattermost/commit/8738f8c4b3d42b2b687a6231e72f313357a2e891","https://mattermost.com/security-updates"],"severity":{"label":"medium","score":4.3},"sources":[{"source":"osv","source_id":"GO-2026-5256","url":"https://osv.dev/vulnerability/GO-2026-5256"},{"source":"nvd","source_id":"CVE-2026-28759","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-28759"}],"summary":"Mattermost does not verify remote cluster channel access when processing shared channel membership removals in github.com/mattermost/mattermost-server"}