Vulnerability Description
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.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Caddyserver | Caddy | < 2.11.4 |
Related Weaknesses (CWE)
References
- https://github.com/caddyserver/caddy/security/advisories/GHSA-f59h-q822-g45gExploitThird Party Advisory
- https://access.redhat.com/security/cve/CVE-2026-52845
- https://bugzilla.redhat.com/show_bug.cgi?id=2491907
- https://github.com/caddyserver/caddy/security/advisories/GHSA-f59h-q822-g45gExploitThird Party Advisory
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-52845.json
FAQ
What is CVE-2026-52845?
CVE-2026-52845 is a vulnerability with a CVSS score of 8.1 (HIGH). 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 ...
How severe is CVE-2026-52845?
CVE-2026-52845 has been rated HIGH with a CVSS base score of 8.1/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-52845?
Check the references section above for vendor advisories and patch information. Affected products include: Caddyserver Caddy.