CVE-2025-41733: Metz-connect Ewio2-m Auth Bypass Flaw

CVE-2025-41733 Overview

CVE-2025-41733 is a critical authentication bypass vulnerability affecting METZ CONNECT EWIO2 series industrial IoT devices. The commissioning wizard on affected devices fails to validate whether the device has already been initialized, allowing unauthenticated remote attackers to construct POST requests that can set root credentials. This flaw enables complete device takeover without any prior authentication.

Critical Impact

Unauthenticated remote attackers can gain root-level access to affected METZ CONNECT EWIO2 devices by exploiting the commissioning wizard to set arbitrary root credentials, potentially compromising entire industrial control environments.

Affected Products

• METZ CONNECT EWIO2-M (all firmware versions)
• METZ CONNECT EWIO2-M-BM (all firmware versions)
• METZ CONNECT EWIO2-BM (all firmware versions)

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

This vulnerability stems from a fundamental flaw in the device initialization workflow. The commissioning wizard, designed to guide administrators through initial device setup, does not implement proper state validation to determine if the device has already completed the initialization process. As a result, the wizard remains accessible even after the device is fully configured and operational.

The vulnerability is classified under CWE-305 (Authentication Bypass by Primary Weakness), indicating that the core authentication mechanism can be circumvented entirely. An attacker with network access to the affected device can exploit this flaw to reset or override root credentials without needing to authenticate first.

The network-accessible nature of this vulnerability, combined with the lack of authentication requirements and the ability to gain root access, makes this a particularly dangerous flaw for industrial environments where these devices may be deployed.

Root Cause

The root cause of CVE-2025-41733 lies in the improper implementation of the commissioning wizard's access control logic. The firmware fails to maintain or check a persistent flag indicating that initial device setup has been completed. This allows the commissioning endpoints to remain accessible and functional indefinitely, regardless of the device's operational state.

The absence of authentication checks on POST requests to the commissioning wizard endpoints enables attackers to invoke credential-setting functions that should only be available during legitimate first-time device configuration.

Attack Vector

The attack vector for this vulnerability is network-based and requires no user interaction or prior authentication. An attacker can exploit this flaw by:

1. Identifying an exposed METZ CONNECT EWIO2 device on the network
2. Accessing the commissioning wizard interface via HTTP/HTTPS
3. Constructing malicious POST requests to the credential-setting endpoints
4. Setting new root credentials of the attacker's choosing
5. Authenticating with the newly created credentials to gain full device control

The attack can be performed remotely from anywhere with network access to the target device. Once root credentials are established, the attacker has complete control over the device, including the ability to modify configurations, intercept data, or use the device as a pivot point for further attacks on the industrial network.

Detection Methods for CVE-2025-41733

Indicators of Compromise

• Unexpected HTTP POST requests to commissioning wizard endpoints from external or unauthorized IP addresses
• Sudden changes in root account credentials or creation of new administrative accounts
• Unusual access patterns to device configuration interfaces outside of maintenance windows
• Authentication logs showing successful root logins from previously unknown sources

Detection Strategies

• Monitor network traffic for POST requests targeting commissioning or setup endpoints on EWIO2 devices
• Implement network segmentation monitoring to detect unauthorized access attempts to industrial IoT device management interfaces
• Deploy intrusion detection rules to alert on credential modification attempts from non-administrative sources
• Review device authentication logs regularly for anomalous login activity

Monitoring Recommendations

• Establish baseline network behavior for EWIO2 devices and alert on deviations
• Configure SIEM rules to correlate access attempts to commissioning endpoints with source IP reputation data
• Implement logging and alerting for all administrative actions on EWIO2 devices
• Deploy SentinelOne Singularity for network visibility and endpoint protection across the industrial environment

How to Mitigate CVE-2025-41733

Immediate Actions Required

• Isolate affected METZ CONNECT EWIO2 devices from untrusted network segments immediately
• Implement strict network access controls to limit which hosts can communicate with EWIO2 device management interfaces
• Verify current root credentials have not been compromised and reset them if necessary
• Review device logs for any signs of unauthorized access or credential modifications

Patch Information

Consult the CERT-VDE Advisory VDE-2025-097 for official patch information and firmware updates from METZ CONNECT. Organizations should apply vendor-provided security updates as soon as they become available.

Contact METZ CONNECT support for guidance on obtaining and applying firmware updates that address this vulnerability. Prioritize patching for any devices exposed to untrusted networks.

Workarounds

• Place all affected EWIO2 devices behind a firewall or VPN that restricts access to authorized administrators only
• Disable or block network access to the commissioning wizard endpoints at the network perimeter if supported by your infrastructure
• Implement additional authentication layers such as VPN or jump hosts for accessing device management interfaces
• Monitor commissioning endpoint access and alert on any unexpected requests until patches can be applied

# Network segmentation example using iptables
# Restrict access to EWIO2 devices to specific management hosts

# Allow access only from trusted management subnet
iptables -A INPUT -s 10.0.100.0/24 -d <EWIO2_IP> -p tcp --dport 80 -j ACCEPT
iptables -A INPUT -s 10.0.100.0/24 -d <EWIO2_IP> -p tcp --dport 443 -j ACCEPT

# Drop all other inbound traffic to web management ports
iptables -A INPUT -d <EWIO2_IP> -p tcp --dport 80 -j DROP
iptables -A INPUT -d <EWIO2_IP> -p tcp --dport 443 -j DROP