{"action":"Upgrade github.com/mattermost/mattermost-server to 5.3.2-0.20260327001745-7a339a6438f5 or later.","affected":[{"fixed":"5.3.2-0.20260327001745-7a339a6438f5","introduced":"0"}],"component":"github.com/mattermost/mattermost-server","cve_ids":["CVE-2026-6339"],"ecosystem":"Go","epss":0.00157,"exploited":false,"fixed_versions":["5.3.2-0.20260327001745-7a339a6438f5"],"ghsa_id":"GHSA-xvcx-mgpc-5xh3","id":"tcs_01M5KFSSD886ASYX9W699XT94W","modified_at":"2026-06-25T23:11:08.526631477Z","published_at":"2026-05-18T09:31:48Z","references":["https://osv.dev/vulnerability/GHSA-xvcx-mgpc-5xh3","https://nvd.nist.gov/vuln/detail/CVE-2026-6339","https://github.com/mattermost/mattermost/commit/7a339a6438f5a4a5feba6b8de887f17a1378b207","https://github.com/mattermost/mattermost","https://mattermost.com/security-updates"],"severity":{"label":"medium","score":4.3},"sources":[{"source":"osv","source_id":"GHSA-xvcx-mgpc-5xh3#Go/github.com/mattermost/mattermost-server","url":"https://osv.dev/vulnerability/GHSA-xvcx-mgpc-5xh3"}],"summary":"Mattermost doesn't validate the X-Requested-With header on the burn-on-read reveal endpoint"}