{"action":"Upgrade github.com/mattermost/mattermost/server/v8 to 8.0.0-20260327001745-7a339a6438f5 or later.","affected":[{"fixed":"8.0.0-20260327001745-7a339a6438f5","introduced":"0"}],"component":"github.com/mattermost/mattermost/server/v8","cve_ids":["CVE-2026-6339"],"ecosystem":"Go","epss":0.00113,"exploited":false,"fixed_versions":["8.0.0-20260327001745-7a339a6438f5"],"ghsa_id":"GHSA-xvcx-mgpc-5xh3","id":"tcs_01M5KGPT348MZEZA4K5N4GREN1","modified_at":"2026-06-25T23:01:41.269315004Z","published_at":"2026-06-25T22:34:41Z","references":["https://osv.dev/vulnerability/GO-2026-5769","https://github.com/advisories/GHSA-xvcx-mgpc-5xh3","https://nvd.nist.gov/vuln/detail/CVE-2026-6339","https://github.com/mattermost/mattermost/commit/7a339a6438f5a4a5feba6b8de887f17a1378b207","https://mattermost.com/security-updates"],"severity":{"label":"medium","score":4.3},"sources":[{"source":"osv","source_id":"GO-2026-5769#Go/github.com/mattermost/mattermost/server/v8","url":"https://osv.dev/vulnerability/GO-2026-5769"},{"source":"nvd","source_id":"CVE-2026-6339","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-6339"}],"summary":"Mattermost doesn't validate the X-Requested-With header on the burn-on-read reveal endpoint in github.com/mattermost/mattermost-server"}