CVE-2025-9495: Viessmann Vitogate 300

High severity, CVSS 8.7. EPSS: 0.2% chance of exploitation in the next 30 days.

The Vitogate 300 web interface fails to enforce proper server-side authentication and relies on frontend-based authentication controls. This allows an attacker to simply modify HTML elements in the browser’s developer tools to bypass login restrictions. By removing specific UI elements, an attacker can reveal the hidden administration menu, giving them full control over the device.

Affected products

• Viessmann Vitogate 300: from 1, before 3.0.0.0 (fixed in 3.0.0.0)

Published 2025-09-23. Last modified 2026-06-17.