{"id":"CVE-2026-4054","aliases":["GHSA-j76w-p754-g2w7","GO-2026-5454"],"url":"https://o3.security/vulnerability/CVE-2026-4054","summary":"SVG content served through Mattermost image proxy despite Content-Type restrictions causes client-side denial of service","details":"Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 Fail to validate the response body of proxied images, which allows a remote attacker to enact client-side DoS via an SVG file served from an attacker-controlled origin under a non-SVG Content-Type header (e.g. image/png) embedded in an og:image meta tag or Markdown image link.. Mattermost Advisory ID: MMSA-2026-00630","published":"2026-05-15T18:32:44.388Z","modified":"2026-08-12T03:51:11.960817213Z","cvss":{"score":4.3,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L"},"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Go","name":"github.com/mattermost/mattermost-server","fixedVersion":"11.5.2"},{"ecosystem":"Go","name":"github.com/mattermost/mattermost-server","fixedVersion":"0.0.0-20260414103857-b21ef302025e"},{"ecosystem":"Go","name":"github.com/mattermost/mattermost-server","fixedVersion":"11.4.4"}],"fix":null,"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/4xxx/CVE-2026-4054.json"},{"type":"ADVISORY","url":"https://mattermost.com/security-updates"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-4054"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:11.960817213Z"}}