{"id":"GHSA-j76w-p754-g2w7","summary":"Mattermost doesn't validate the response body of proxied images","details":"Mattermost versions 11.5.x \u003c= 11.5.1, 10.11.x \u003c= 10.11.13, 11.4.x \u003c= 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.","aliases":["CVE-2026-4054","GO-2026-5454"],"modified":"2026-06-25T23:11:17.437906978Z","published":"2026-05-15T21:31:33Z","database_specific":{"nvd_published_at":"2026-05-15T19:17:04Z","cwe_ids":["CWE-754"],"severity":"MODERATE","github_reviewed":true,"github_reviewed_at":"2026-05-28T19:28:48Z"},"references":[{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-4054"},{"type":"PACKAGE","url":"https://github.com/mattermost/mattermost"},{"type":"WEB","url":"https://mattermost.com/security-updates"}],"affected":[{"package":{"name":"github.com/mattermost/mattermost-server","ecosystem":"Go","purl":"pkg:golang/github.com/mattermost/mattermost-server"},"ranges":[{"type":"SEMVER","events":[{"introduced":"11.5.0"},{"fixed":"11.5.2"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-j76w-p754-g2w7/GHSA-j76w-p754-g2w7.json"}},{"package":{"name":"github.com/mattermost/mattermost-server","ecosystem":"Go","purl":"pkg:golang/github.com/mattermost/mattermost-server"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0.0.0-20250731163400-5b955468ea1e"},{"fixed":"0.0.0-20260414103857-b21ef302025e"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-j76w-p754-g2w7/GHSA-j76w-p754-g2w7.json"}},{"package":{"name":"github.com/mattermost/mattermost-server","ecosystem":"Go","purl":"pkg:golang/github.com/mattermost/mattermost-server"},"ranges":[{"type":"SEMVER","events":[{"introduced":"11.4.0"},{"fixed":"11.4.4"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-j76w-p754-g2w7/GHSA-j76w-p754-g2w7.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L"}]}