{"action":"Upgrade github.com/mattermost/mattermost-server to 0.0.0-20260414103857-b21ef302025e or later.","affected":[{"fixed":"11.5.2","introduced":"11.5.0"},{"fixed":"0.0.0-20260414103857-b21ef302025e","introduced":"0.0.0-20250731163400-5b955468ea1e"},{"fixed":"11.4.4","introduced":"11.4.0"}],"component":"github.com/mattermost/mattermost-server","cve_ids":["CVE-2026-4054"],"ecosystem":"Go","epss":0.00242,"exploited":false,"fixed_versions":["11.5.2","0.0.0-20260414103857-b21ef302025e","11.4.4"],"ghsa_id":"GHSA-j76w-p754-g2w7","id":"tcs_01M5KFDPNFMZ51NGBJ4QHD4F45","modified_at":"2026-06-25T23:11:39.197468242Z","published_at":"2026-05-15T21:31:33Z","references":["https://osv.dev/vulnerability/GHSA-j76w-p754-g2w7","https://nvd.nist.gov/vuln/detail/CVE-2026-4054","https://github.com/mattermost/mattermost","https://mattermost.com/security-updates"],"severity":{"label":"medium","score":4.3},"sources":[{"source":"osv","source_id":"GHSA-j76w-p754-g2w7","url":"https://osv.dev/vulnerability/GHSA-j76w-p754-g2w7"}],"summary":"Mattermost doesn't validate the response body of proxied images"}