Advisory severityHigh8.1Red Hat Linux

High [CVE-2026-52845] Remote client can inject or override identity headers via header normalization

This high-severity Red Hat Linux advisory covers CVE-2026-52845.

Aggregated and source-linked by VulniPulse. Data sources, validation and limitations.

CVE-2026-52845 Source published Jun 23, 2026Source updated Jun 23, 2026

VulniPulse record published Jul 6, 2026Record updated Jul 13, 2026

CVE-2026-52845

Affected products & platforms

Red Hat LinuxUnclassified

Open source advisory

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Summary

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 remote attacker can exploit a vulnerability in the `forward_auth` `copy_headers` functionality. Red Hat severity: Important — CVSS 8.1 (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N).

Weakness: CWE-444. Red Hat lists Red Hat Hardened Images as not affected.

Affected versions

< 2.11.4

Official advisory · high-confidence parse· fetched 21 days ago·verify at source

Fixed versions

2.11.4

Official advisory · high-confidence parse· fetched 21 days ago·verify at source

Mitigation

Upgrade to a fixed release: 2.11.4. That is the remediation for this advisory.

The vendor advisory may list additional interim mitigations or workarounds not captured here — review it before change work.

Official advisory · high-confidence parse· fetched 21 days ago·verify at source

Discussion(0)

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