{"action":"Upgrade github.com/mattermost/mattermost-server to 10.11.12+incompatible or later.","affected":[{"fixed":"10.11.12+incompatible","introduced":"10.11.0-rc1+incompatible"},{"fixed":"11.2.4+incompatible","introduced":"11.2.0-rc1+incompatible"},{"fixed":"11.3.2+incompatible","introduced":"11.3.0-rc1+incompatible"},{"fixed":"11.4.1+incompatible","introduced":"11.4.0-rc1+incompatible"}],"component":"github.com/mattermost/mattermost-server","cve_ids":["CVE-2026-27656"],"ecosystem":"Go","epss":0.00183,"exploited":false,"fixed_versions":["10.11.12+incompatible","11.2.4+incompatible","11.3.2+incompatible","11.4.1+incompatible"],"ghsa_id":"GHSA-fg35-5rf6-qg3g","id":"tcs_01M5KGKRZ80EPK1CY483MY2KE6","modified_at":"2026-06-25T19:45:34.725735565Z","published_at":"2026-06-25T18:43:19Z","references":["https://osv.dev/vulnerability/GO-2026-5360","https://github.com/advisories/GHSA-fg35-5rf6-qg3g","https://nvd.nist.gov/vuln/detail/CVE-2026-27656","https://mattermost.com/security-updates"],"severity":{"label":"medium","score":6.1},"sources":[{"source":"osv","source_id":"GO-2026-5360","url":"https://osv.dev/vulnerability/GO-2026-5360"},{"source":"nvd","source_id":"CVE-2026-27656","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-27656"}],"summary":"Mattermost allows attackers to take over arbitrary user accounts via overly permissive substring matching flaw in github.com/mattermost/mattermost-server"}