{"id":"UBUNTU-CVE-2026-52845","details":"Caddy is an extensible server platform that uses TLS by default. Prior to 2.11.4, forward_auth copy_headers deletes the exact client-supplied identity header before copying the trusted value from the auth gateway. But when the request later goes through php_fastcgi, Caddy normalizes HTTP headers into CGI variables by replacing - with _. This lets a client send an underscore alias that survives the forward_auth delete step but becomes the same PHP/FastCGI variable. Result: a remote client can inject or sometimes override identity/group headers trusted by PHP/FastCGI applications behind Caddy. This vulnerability is fixed in 2.11.4.","modified":"2026-07-02T18:04:18.004154056Z","published":"2026-06-23T18:18:00Z","upstream":["CVE-2026-52845"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-52845"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-52845"}],"affected":[{"package":{"name":"caddy","ecosystem":"Ubuntu:Pro:24.04:LTS","purl":"pkg:deb/ubuntu/caddy?arch=source&distro=esm-apps%2Fnoble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.6.2-6","2.6.2-6ubuntu0.24.04.1","2.6.2-6ubuntu0.24.04.2","2.6.2-6ubuntu0.24.04.2+esm1","2.6.2-6ubuntu0.24.04.3","2.6.2-6ubuntu0.24.04.3+esm1","2.6.2-6ubuntu0.24.04.3+esm2"],"ecosystem_specific":{"binaries":[{"binary_version":"2.6.2-6ubuntu0.24.04.3+esm2","binary_name":"caddy"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-52845.json"}},{"package":{"name":"caddy","ecosystem":"Ubuntu:25.10","purl":"pkg:deb/ubuntu/caddy?arch=source&distro=questing"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.6.2-9","2.6.2-11","2.6.2-12"],"ecosystem_specific":{"binaries":[{"binary_name":"caddy","binary_version":"2.6.2-12"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-52845.json"}},{"package":{"name":"caddy","ecosystem":"Ubuntu:Pro:26.04:LTS","purl":"pkg:deb/ubuntu/caddy?arch=source&distro=esm-apps%2Fresolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.6.2-12","2.6.2-14","2.6.2-14ubuntu0.26.04.1~esm1"],"ecosystem_specific":{"binaries":[{"binary_name":"caddy","binary_version":"2.6.2-14ubuntu0.26.04.1~esm1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-52845.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N"},{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N"},{"type":"Ubuntu","score":"medium"}]}