---
cve: "CVE-2025-66491"
severity: "MEDIUM"
cvss: 5.9
epss: "22%"
vendor: "traefik"
kev: false
exploited: false
published: "2025-12-09 01:16:55"
tags: [cve, security, medium]
source: tsecurity.de CVE-Dossier
exported: "2026-09-17T13:46:35+02:00"
---

# CVE-2025-66491

> 5.9 MEDIUM · 🧪 PoC

## Beschreibung

Traefik is an HTTP reverse proxy and load balancer. Versions 3.5.0 through 3.6.2 have inverted TLS verification logic in the nginx.ingress.kubernetes.io/proxy-ssl-verify annotation. Setting the annotation to "on" (intending to enable backend TLS certificate verification) actually disables verification, allowing man-in-the-middle attacks against HTTPS backends when operators believe they are protected. This issue is fixed in version 3.6.3.

## CVSS-Vektor

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

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

## Patch verfügbar (OSV)

- 8a621274b81cd177ea5f6e07a5d5472af7d213b3 (Commit)
- 14a1aedf5704673d875d210d7bacf103a43c77e4 (Commit)

## Referenzen

- <https://github.com/traefik/traefik/security/advisories/GHSA-7vww-mvcr-x6vj>
- <https://github.com/traefik/traefik/commit/14a1aedf5704673d875d210d7bacf103a43c77e4>
- <https://github.com/traefik/traefik/releases/tag/v3.6.3>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2025-66491) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_