{"schema_version":"1.3.1","id":"GO-2026-5360","modified":"2026-06-25T18:43:19Z","published":"2026-06-25T18:43:19Z","aliases":["CVE-2026-27656","GHSA-fg35-5rf6-qg3g"],"summary":"Mattermost allows attackers to take over arbitrary user accounts via overly permissive substring matching flaw in github.com/mattermost/mattermost-server","details":"Mattermost allows attackers to take over arbitrary user accounts via overly permissive substring matching flaw in github.com/mattermost/mattermost-server","affected":[{"package":{"name":"github.com/mattermost/mattermost-server","ecosystem":"Go"},"ranges":[{"type":"SEMVER","events":[{"introduced":"10.11.0-rc1+incompatible"},{"fixed":"10.11.12+incompatible"},{"introduced":"11.2.0-rc1+incompatible"},{"fixed":"11.2.4+incompatible"},{"introduced":"11.3.0-rc1+incompatible"},{"fixed":"11.3.2+incompatible"},{"introduced":"11.4.0-rc1+incompatible"},{"fixed":"11.4.1+incompatible"}]}],"ecosystem_specific":{}},{"package":{"name":"github.com/mattermost/mattermost-server/v5","ecosystem":"Go"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"}]}],"ecosystem_specific":{}},{"package":{"name":"github.com/mattermost/mattermost-server/v6","ecosystem":"Go"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"}]}],"ecosystem_specific":{}},{"package":{"name":"github.com/mattermost/mattermost/server/v8","ecosystem":"Go"},"ranges":[{"type":"SEMVER","events":[{"introduced":"8.0.0-20260105080200-d27a2195068d"},{"fixed":"8.0.0-20260217110922-b7d4a1f1f59b"}]}],"ecosystem_specific":{}}],"references":[{"type":"ADVISORY","url":"https://github.com/advisories/GHSA-fg35-5rf6-qg3g"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-27656"},{"type":"WEB","url":"https://mattermost.com/security-updates"}],"database_specific":{"url":"https://pkg.go.dev/vuln/GO-2026-5360","review_status":"UNREVIEWED"}}