CVE-2025-41733 Overview
CVE-2025-41733 is an authentication bypass vulnerability in Metz Connect EWIO2 series devices. The commissioning wizard fails to validate whether a device has already been initialized. An unauthenticated remote attacker can send crafted HTTP POST requests to the commissioning endpoint to set root credentials on a deployed device. This grants the attacker full administrative control over the affected device. The flaw is tracked under CWE-305: Authentication Bypass by Primary Weakness and affects the EWIO2-M, EWIO2-M-BM, and EWIO2-BM building automation controllers.
Critical Impact
Remote unauthenticated attackers can take over EWIO2 devices by setting their own root credentials, enabling complete compromise of building automation and energy monitoring infrastructure.
Affected Products
- Metz Connect EWIO2-M (firmware)
- Metz Connect EWIO2-M-BM (firmware)
- Metz Connect EWIO2-BM (firmware)
Discovery Timeline
- 2025-11-18 - CVE-2025-41733 published to NVD
- 2025-11-21 - Last updated in NVD database
Technical Details for CVE-2025-41733
Vulnerability Analysis
The EWIO2 series are web-managed energy monitoring and building automation controllers. Initial provisioning is performed through a commissioning wizard exposed by the device's embedded web interface. The wizard accepts POST requests that configure the root account credentials during first-time setup.
The vulnerability stems from the wizard not checking the device's initialization state before accepting credential-setting requests. A device that has already been commissioned still accepts unauthenticated POST requests to the commissioning endpoint. An attacker reaching the management interface over the network can overwrite the existing root password without supplying current credentials.
Once credentials are reset, the attacker authenticates as root and gains administrative control. This permits manipulation of building automation logic, data exfiltration from connected sensors, lateral movement into operational technology networks, and persistent device implantation.
Root Cause
The commissioning routine lacks a state check that confirms whether initial setup has already completed. Authentication is treated as a one-time enrollment event rather than a persistent property of the device. This design omission corresponds to [CWE-305], where the authentication mechanism can be bypassed because a required precondition is not enforced.
Attack Vector
Exploitation requires network access to the device's HTTP management interface and no prior authentication or user interaction. The attacker issues a POST request to the commissioning endpoint with attacker-chosen credentials. The device persists the new credentials and grants the attacker administrative access on subsequent logins. Devices exposed directly to the internet or reachable from compromised IT segments are at highest risk.
For technical specifics, see the CERT VDE Advisory VDE-2025-097.
Detection Methods for CVE-2025-41733
Indicators of Compromise
- Unexpected POST requests to the commissioning wizard URL on EWIO2 devices after initial deployment
- Unplanned changes to the device root account or password hash
- Successful root logins from unfamiliar source IP addresses following a commissioning request
- New or modified automation rules, schedules, or outbound connections originating from the device
Detection Strategies
- Inspect web server access logs on EWIO2 devices for HTTP POST traffic to commissioning paths outside of authorized provisioning windows
- Alert on authentication events for the root account from non-administrative source networks
- Monitor configuration baselines and flag deviations in user account metadata or device identity files
Monitoring Recommendations
- Forward EWIO2 device logs and management network flow data to a central SIEM for correlation
- Track north-south and east-west traffic to the OT segment hosting EWIO2 controllers
- Establish a known-good firmware and configuration baseline and alert on drift
How to Mitigate CVE-2025-41733
Immediate Actions Required
- Restrict network access to EWIO2 management interfaces to trusted administrative hosts using firewall or VLAN segmentation
- Remove any internet exposure of EWIO2 web interfaces and place the devices behind a VPN or jump host
- Audit existing devices for unauthorized credential changes and rotate root passwords on all units
- Apply the firmware update from Metz Connect as soon as it becomes available per the vendor advisory
Patch Information
Metz Connect has coordinated disclosure through CERT@VDE. Refer to the CERT VDE Advisory VDE-2025-097 for the authoritative list of fixed firmware versions and update procedures. Apply the corrected firmware to all EWIO2-M, EWIO2-M-BM, and EWIO2-BM devices in service.
Workarounds
- Place EWIO2 devices on isolated OT network segments with strict ingress filtering
- Block external access to the device HTTP/HTTPS management ports at the perimeter firewall
- Require VPN authentication for any administrative access to building automation controllers
- Monitor commissioning endpoints for POST activity until patched firmware is deployed
# Example: restrict access to EWIO2 management interface using iptables
# Replace 10.10.20.0/24 with your administrative subnet
# Replace 192.0.2.50 with the EWIO2 device IP
iptables -A FORWARD -s 10.10.20.0/24 -d 192.0.2.50 -p tcp --dport 443 -j ACCEPT
iptables -A FORWARD -d 192.0.2.50 -p tcp --dport 443 -j DROP
iptables -A FORWARD -d 192.0.2.50 -p tcp --dport 80 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
