---
cve: "CVE-2026-52845"
severity: "HIGH"
cvss: 8.1
epss: "29%"
vendor: "caddyserver"
kev: false
exploited: false
published: "2026-06-23 18:18:05"
tags: [cve, security, high]
source: tsecurity.de CVE-Dossier
exported: "2026-09-17T06:59:26+02:00"
---

# CVE-2026-52845

> 8.1 HIGH · 🧪 PoC

## Beschreibung

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-Vektor

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

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Gering | bad |
| PR Privilegien | Gering | warn |
| UI Interaktion | Keine | bad |
| S Scope | Unverändert | good |
| C Vertraulichkeit | Hoch | bad |
| I Integrität | Hoch | bad |
| A Verfügbarkeit | Keine | good |

## Patch verfügbar (OSV)

- e2eee6a7fce366321294c9c2a79f3146891dcbdf (Commit)

## Referenzen

- <https://github.com/caddyserver/caddy/security/advisories/GHSA-f59h-q822-g45g>
- <https://access.redhat.com/security/cve/CVE-2026-52845>
- <https://bugzilla.redhat.com/show_bug.cgi?id=2491907>
- <https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-52845.json>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-52845) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_