CVE-2026-52845

HighCVSS 8.1/10Last modified Jul 15, 2026

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.

Metrics

CVSS 3.1 8.1/10CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

Weakness enumeration

CWE-287 CWE-290 CWE-444

Affected software

No affected versions have been published.

Timeline

Published: Jun 23, 2026
Last modified: Jul 15, 2026
NVD status: Modified

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