{"id":"CVE-2019-20866","details":"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.","modified":"2026-04-10T04:17:14.404495Z","published":"2020-06-19T16:15:10.267Z","references":[{"type":"ADVISORY","url":"https://mattermost.com/security-updates/"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/mattermost/mattermost-server","events":[{"introduced":"0"},{"fixed":"bfd66aa445a2df8c6ed6ba9f2567021ecf6c9f3b"}],"database_specific":{"versions":[{"introduced":"0"},{"fixed":"5.12.0"}]}}],"versions":["v0.5.0","v4.10.0-rc1","v4.2.0-rc1","v4.3.0-rc1","v4.4.0-rc1","v4.5.0-rc1","v4.6.0-rc1","v4.6.0-rc2","v4.7.0-rc1","v4.8.0-rc1","v4.9.0-rc1","v5.0.0-rc1","v5.1.0-rc1","v5.12.0-rc1","v5.12.0-rc2","v5.12.0-rc3","v5.12.0-rc4","v5.12.0-rc5","v5.2.0-rc1","v5.2.0-rc2"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2019-20866.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N"}]}