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.

CVSS v3 8.1 HIGH

8.1^/10

CVSS v3 : HIGH

Vector :

Exploitability : 2.8 / Impact : 5.2

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required LOW

User Interaction NONE

Confidentiality Impact HIGH

Integrity Impact HIGH

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://github.com/caddyserver/caddy/security/advisories/GHSA-f59h-q822-g45g	Exploit Third 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-g45g	Exploit Third Party Advisory
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-52845.json

Configurations

Configuration 1 (hide)

cpe:2.3:a:caddyserver:caddy:*:*:*:*:*:*:*:*

History

No history.

Information

Published : 2026-06-23 18:18

Updated : 2026-07-15 01:16

NVD link : CVE-2026-52845

Mitre link : CVE-2026-52845

CVE.ORG link : CVE-2026-52845

JSON object : View

Products Affected

caddyserver

caddy

CWE

CWE-287

Improper Authentication

CWE-290

Authentication Bypass by Spoofing

CWE-444

Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')

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