{"id":"CVE-2017-18911","aliases":["GHSA-m462-mqw4-2c8m","GO-2026-4464"],"url":"https://o3.security/vulnerability/CVE-2017-18911","summary":"Mattermost Server has X.509 Improper Certificate Validation","details":"An issue was discovered in Mattermost Server before 3.8.2, 3.7.5, and 3.6.7. The X.509 certificate validation can be skipped for a TLS-based e-mail server.","published":"2020-06-19T19:15:11.937Z","modified":"2026-07-31T18:30:52.110817893Z","cvss":{"score":9.1,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Go","name":"github.com/mattermost/mattermost-server","fixedVersion":"3.6.7-rc1"},{"ecosystem":"Go","name":"github.com/mattermost/mattermost-server","fixedVersion":"3.7.5"},{"ecosystem":"Go","name":"github.com/mattermost/mattermost-server","fixedVersion":"3.8.2"}],"fix":null,"references":[{"type":"ADVISORY","url":"https://mattermost.com/security-updates/"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-07-31T18:30:52.110817893Z"}}