{"action":"Upgrade github.com/mattermost/mattermost/server/v8 to 8.0.0-20260410202636-17939826efa2 or later.","affected":[{"fixed":"8.0.0-20260410202636-17939826efa2","introduced":"0"}],"component":"github.com/mattermost/mattermost/server/v8","cve_ids":["CVE-2026-5740"],"ecosystem":"Go","epss":0.0034,"exploited":false,"fixed_versions":["8.0.0-20260410202636-17939826efa2"],"ghsa_id":"GHSA-w9m8-p4cc-4qj9","id":"tcs_01M5KGQ6JXMV3PE5ZK8NENH5K4","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":"high","score":7.5},"sources":[{"source":"osv","source_id":"GO-2026-5838#Go/github.com/mattermost/mattermost/server/v8","url":"https://osv.dev/vulnerability/GO-2026-5838"},{"source":"nvd","source_id":"CVE-2026-5740","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-5740"}],"summary":"Mattermost doesn't properly validate msgpack-encoded WebSocket frames before memory allocation in github.com/mattermost/mattermost-server"}