{"action":"Upgrade github.com/mattermost/mattermost-server to 10.11.15 or later.","affected":[{"fixed":"11.6.1","introduced":"11.6.0"},{"fixed":"11.5.4","introduced":"11.5.0"},{"fixed":"11.4.5","introduced":"11.4.0"},{"fixed":"10.11.15","introduced":"10.11.0"}],"component":"github.com/mattermost/mattermost-server","cve_ids":["CVE-2026-5740"],"ecosystem":"Go","epss":0.0034,"exploited":false,"fixed_versions":["11.6.1","11.5.4","11.4.5","10.11.15"],"ghsa_id":"GHSA-w9m8-p4cc-4qj9","id":"tcs_01M5KFQJAH476DDDSD2EAW0VAQ","modified_at":"2026-07-07T16:11:10.343209548Z","published_at":"2026-05-26T13:30:15Z","references":["https://osv.dev/vulnerability/GHSA-w9m8-p4cc-4qj9","https://nvd.nist.gov/vuln/detail/CVE-2026-5740","https://github.com/mattermost/mattermost/commit/17939826efa20a97f087b3d390ec5136df350bae","https://github.com/mattermost/mattermost","https://mattermost.com/security-updates"],"severity":{"label":"high","score":7.5},"sources":[{"source":"osv","source_id":"GHSA-w9m8-p4cc-4qj9","url":"https://osv.dev/vulnerability/GHSA-w9m8-p4cc-4qj9"}],"summary":"Mattermost doesn't properly validate msgpack-encoded WebSocket frames before memory allocation"}