{"id":"CVE-2019-20866","aliases":["EUVD-2019-11403","GHSA-mmmh-x6gq-25cg"],"status":"published","title":"An issue was discovered in Mattermost Server before 5.12.0. Use of a Proxy HTTP header, rather...","description":"An issue was discovered in Mattermost Server before 5.12.0. Use of a Proxy HTTP header, rather than the source address in an IP packet header, for obtaining IP address information was mishandled.","severity":{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N","level":"medium","assessor":"primary","from":"nvd"},"epss":{"day":"2026-11-09","score":0.0092,"percentile":0.60532,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-444"],"published":"2020-06-19T15:13:15Z","modified":"2026-10-24T10:30:54Z","products":[{"vendor":"mattermost","product":"mattermost_server"}],"references":[{"url":"https://mattermost.com/security-updates/","tags":["x_refsource_CONFIRM","x_transferred","Vendor Advisory","advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2019-20866"},{"url":"https://github.com/advisories/GHSA-mmmh-x6gq-25cg"}],"sources":{"cve":[{"id":"CVE-2019-20866","description":"An issue was discovered in Mattermost Server before 5.12.0. Use of a Proxy HTTP header, rather than the source address in an IP packet header, for obtaining IP address information was mishandled.","status":"published","published":"2020-06-19T15:13:15Z","modified":"2024-08-05T02:53:09.422Z","updated_at":"2026-11-02T14:20:17.431882Z"}],"euvd":[{"id":"EUVD-2019-11403","description":"An issue was discovered in Mattermost Server before 5.12.0. Use of a Proxy HTTP header, rather than the source address in an IP packet header, for obtaining IP address information was mishandled.","status":"published","published":"2020-06-19T15:13:15Z","modified":"2024-08-05T02:53:09Z","updated_at":"2026-11-03T02:40:20.270172Z"}],"ghsa":[{"id":"GHSA-mmmh-x6gq-25cg","title":"An issue was discovered in Mattermost Server before 5.12.0. Use of a Proxy HTTP header, rather...","description":"An issue was discovered in Mattermost Server before 5.12.0. Use of a Proxy HTTP header, rather than the source address in an IP packet header, for obtaining IP address information was mishandled.","status":"published","published":"2022-05-24T17:21:12Z","modified":"2023-01-29T05:03:06Z","updated_at":"2026-11-02T14:45:14.655741Z"}],"nvd":[{"id":"CVE-2019-20866","description":"An issue was discovered in Mattermost Server before 5.12.0. Use of a Proxy HTTP header, rather than the source address in an IP packet header, for obtaining IP address information was mishandled.","status":"published","published":"2020-06-19T16:15:10.267Z","modified":"2026-06-17T02:31:20.69Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N","level":"medium","assessor":"primary"},{"version":"2.0","score":5,"vector":"AV:N/AC:L/Au:N/C:P/I:N/A:N","level":"medium","assessor":"primary"}],"cwes":["CWE-444"],"updated_at":"2026-11-02T14:05:47.558959Z"}],"osv":[{"id":"CVE-2019-20866","description":"An issue was discovered in Mattermost Server before 5.12.0. Use of a Proxy HTTP header, rather than the source address in an IP packet header, for obtaining IP address information was mishandled.","status":"published","published":"2020-06-19T16:15:10.267Z","modified":"2026-10-24T10:30:54.833029977Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N","level":"medium"}],"updated_at":"2026-11-02T15:44:12.010761Z"}]}}