{"action":"Upgrade github.com/mattermost/mattermost-server to 10.11.15+incompatible or later.","affected":[{"fixed":"10.11.15+incompatible","introduced":"10.11.0+incompatible"},{"fixed":"11.4.5+incompatible","introduced":"11.4.0+incompatible"},{"fixed":"11.5.4+incompatible","introduced":"11.5.0+incompatible"},{"fixed":"11.6.1+incompatible","introduced":"11.6.0+incompatible"}],"component":"github.com/mattermost/mattermost-server","cve_ids":["CVE-2026-5740"],"ecosystem":"Go","epss":0.00573,"exploited":false,"fixed_versions":["10.11.15+incompatible","11.4.5+incompatible","11.5.4+incompatible","11.6.1+incompatible"],"ghsa_id":"GHSA-w9m8-p4cc-4qj9","id":"tcs_01M5KGQ6246KPD5BSP5PAFSGDA","modified_at":"2026-07-07T16:01:34.665634742Z","published_at":"2026-07-07T15:26:32Z","references":["https://osv.dev/vulnerability/GO-2026-5838","https://github.com/advisories/GHSA-w9m8-p4cc-4qj9","https://nvd.nist.gov/vuln/detail/CVE-2026-5740","https://github.com/mattermost/mattermost/commit/17939826efa20a97f087b3d390ec5136df350bae","https://mattermost.com/security-updates"],"severity":{"label":"unknown"},"sources":[{"source":"osv","source_id":"GO-2026-5838","url":"https://osv.dev/vulnerability/GO-2026-5838"}],"summary":"Mattermost doesn't properly validate msgpack-encoded WebSocket frames before memory allocation in github.com/mattermost/mattermost-server"}