Critical Authentication Bypass in CHOCO TEI WATCHER mini Exposes Industrial Systems

A critical vulnerability (CVE-2025-25211) affecting all versions of the CHOCO TEI WATCHER mini (IB-MCT001) industrial monitoring device has been disclosed, exposing manufacturing systems to brute-force attacks due to weak password requirements. The flaw, rated 9.8 (CRITICAL) on the CVSS scale, allows unauthorized access to device interfaces without authentication¹. This vulnerability is part of a broader set of security issues identified in the device, including client-side authentication flaws and insecure password storage².

Technical Analysis of the Vulnerability

The CVE-2025-25211 vulnerability stems from weak password policies (CWE-521) that fail to enforce complexity requirements or lockout mechanisms. According to Nozomi Networks researcher Andrea Palanca, who reported the flaws through JPCERT/CC, the device’s web interface accepts simple dictionary passwords without rate limiting³. The authentication system does not implement account lockouts after failed attempts, making brute-force attacks trivial to execute. Successful exploitation grants full access to the device’s configuration interface, where attackers could manipulate production monitoring settings or disable critical alerts.

Testing confirms the vulnerability affects all firmware versions of the IB-MCT001 model. The device’s default credentials (admin/admin) remain active even after initial setup, compounding the risk. Network scans show approximately 1,200 exposed instances globally, primarily in manufacturing facilities across Japan, Germany, and the United States⁴.

Broader Security Implications

This vulnerability forms part of a chain of four critical flaws in the CHOCO TEI WATCHER mini. The most severe combination (CVE-2025-25211 and CVE-2025-26689) could allow remote attackers to bypass authentication and modify device configurations through forced browsing⁵. In industrial environments, this could lead to undetected production line manipulation or suppression of quality control alerts.

Inaba Denki Sangyo Co., the device manufacturer, has acknowledged the issues but has not released firmware patches as of March 2025. The company recommends network isolation as an interim measure while working on updates⁶. CISA’s advisory ICSA-25-084-04 emphasizes that these vulnerabilities are particularly dangerous in OT environments where the devices often operate without firewall protection.

Mitigation Strategies

Organizations using affected devices should implement these immediate countermeasures:

• Segment networks to restrict CHOCO TEI WATCHER mini devices to VLANs with no internet access
• Implement MAC address filtering to limit device communication to authorized hosts
• Enable logging on all HTTP requests to the device web interface
• Replace default credentials with complex passwords (minimum 12 characters with special characters)

For long-term protection, CISA recommends replacing vulnerable devices with models that support modern authentication protocols. Monitoring solutions should be configured to alert on repeated login attempts or configuration changes.

Conclusion

The CHOCO TEI WATCHER mini vulnerabilities demonstrate the persistent risks of weak authentication in industrial IoT devices. With no available patches, organizations must rely on network controls and vigilant monitoring to prevent exploitation. This case highlights the need for stricter security standards in industrial device procurement and the importance of vulnerability disclosure programs in critical infrastructure sectors.