{"id":"CVE-2026-6333","aliases":["GHSA-vqp5-2mrp-qqxg","GO-2026-5671"],"url":"https://o3.security/vulnerability/CVE-2026-6333","summary":"SSRF via Host Header Spoofing in Custom Slash Commands","details":"Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13 fail to validate the Host header when constructing response URLs for custom slash commands which allows an authenticated attacker to redirect slash command responses to an attacker-controlled server via a spoofed Host header.. Mattermost Advisory ID: MMSA-2026-00582","published":"2026-05-18T08:41:29.342Z","modified":"2026-08-12T03:51:45.305170917Z","cvss":{"score":3.5,"severity":"LOW","vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:N/I:L/A:N"},"epss":{"score":0.00137,"percentile":0.03562,"asOf":"2026-08-15"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Go","name":"github.com/mattermost/mattermost/server/v8","fixedVersion":"11.5.2"},{"ecosystem":"Go","name":"github.com/mattermost/mattermost/server/v8","fixedVersion":"10.11.14"},{"ecosystem":"Go","name":"github.com/mattermost/mattermost/server/v8","fixedVersion":"8.0.0-20260325160634-e738016c5920"},{"ecosystem":"Go","name":"github.com/mattermost/mattermost-server","fixedVersion":"5.3.2-0.20260325160634-e738016c5920"}],"fix":null,"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/6xxx/CVE-2026-6333.json"},{"type":"ADVISORY","url":"https://mattermost.com/security-updates"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-6333"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:45.305170917Z"}}