Security Advisory

CVE-2026-52845

CVE vulnerability detail - eXtreme Datacenter Security Operations

Published 2026-06-23 17:52:01

Last updated 2026-07-15 00:46:09

Assigner GitHub_M

CVSS score 8.1

State PUBLISHED

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.

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