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.

Affected products

Caddy

Caddyserver Caddy

< 2.11.4

Fix

Available

CVSS 3.1

8.1 HIGH

EPSS

0.3% (22th percentile)

Weakness

CWE-444, CWE-290, CWE-287

NVD status

Modified

Published

2026-06-23

No exploit for CVE-2026-52845 has been indexed yet. Our index is built from live traffic and upstream syncs, so this page can only say what it knows — not that no exploit exists.