Copyright © 2012 Red Hat, Inc. All rights reserved. Important 2026-06-23T17:52:01 github.com/caddyserver/caddy: Caddy: Remote client can inject or override identity headers via header normalization 8.1 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N CWE-444

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.

A flaw was found in Caddy, an extensible server platform. A remote attacker can exploit a vulnerability in the `forward_auth` `copy_headers` functionality. This occurs because Caddy normalizes HTTP headers into Common Gateway Interface (CGI) variables by replacing hyphens with underscores, allowing a client to send an underscore alias that bypasses the header deletion step. This enables the remote attacker to inject or override identity and group headers trusted by PHP/FastCGI applications operating behind Caddy.

Red Hat Hardened Images Not affected caddy https://www.cve.org/CVERecord?id=CVE-2026-52845 https://nvd.nist.gov/vuln/detail/CVE-2026-52845 https://github.com/caddyserver/caddy/security/advisories/GHSA-f59h-q822-g45g