CVE-2026-52845
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.
- Score
- CVSS 3.1 8.1 High
- Status
- Modified - security-advisories@github.com
- Published
- 2026-06-23
- Last modified
- 2026-10-25
- Weaknesses
- CWE-287, CWE-290, CWE-444
Affected products
References
- https://github.com/caddyserver/caddy/security/advisories/GHSA-f59h-q822-g45g
- https://access.redhat.com/security/cve/CVE-2026-52845
- https://bugzilla.redhat.com/show_bug.cgi?id=2491907
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-52845.json
