CVE-2021-34567 is a high-severity vulnerability identified in the WAGO 750-81xx/xxx-xxxFW series, specifically affecting the WAGO I/O-Check Service. This vulnerability is classified as a CWE-125 Out-of-bounds Read, which occurs when the software reads data outside the bounds of allocated memory. The flaw allows an unauthenticated remote attacker to send specially crafted packets containing operating system commands to the vulnerable service. Exploitation of this vulnerability can provoke a denial of service (DoS) condition by causing the affected device to crash or become unresponsive. Additionally, the out-of-bounds read may lead to limited information disclosure, potentially leaking sensitive memory contents. The vulnerability requires no authentication or user interaction, and can be triggered remotely over the network, making it highly accessible to attackers. The CVSS v3.1 base score is 8.2, reflecting the network attack vector, low attack complexity, no privileges required, and no user interaction needed. The impact primarily affects availability, with a limited impact on confidentiality, and no impact on integrity. The affected product is firmware version FW1 of the WAGO 750-81xx/xxx-xxxFW series, which is commonly used in industrial automation and control systems (ICS) environments. No known exploits have been reported in the wild, and no patches or mitigation links are currently provided by the vendor, indicating that affected organizations must rely on other defensive measures until an official fix is released.

For European organizations, particularly those operating in industrial automation, manufacturing, energy, and critical infrastructure sectors, this vulnerability poses a significant risk. WAGO devices are widely deployed in European industrial environments for process control and monitoring. A successful exploitation could lead to denial of service conditions, disrupting operational technology (OT) systems and potentially halting production lines or critical infrastructure operations. The limited out-of-bounds read may also expose sensitive information that could aid further attacks. Given the unauthenticated and remote nature of the exploit, attackers could leverage this vulnerability to cause operational disruptions without needing prior access or credentials. This could have cascading effects on supply chains and critical services, especially in sectors with high reliance on WAGO devices. The lack of available patches increases the urgency for organizations to implement compensating controls to reduce exposure.

1. Network Segmentation: Isolate WAGO 750-81xx/xxx-xxxFW devices within dedicated OT network segments, restricting access only to trusted management systems and monitoring devices. 2. Access Control Lists (ACLs): Implement strict firewall rules to block unauthorized inbound traffic to the WAGO I/O-Check Service ports from untrusted networks, especially the internet. 3. Intrusion Detection and Prevention: Deploy network-based IDS/IPS solutions configured to detect anomalous packets or command injection attempts targeting WAGO devices. 4. Monitoring and Logging: Enable detailed logging on network gateways and OT management systems to detect unusual traffic patterns or repeated connection attempts to the vulnerable service. 5. Vendor Engagement: Maintain close contact with WAGO for updates on patches or firmware upgrades addressing this vulnerability and plan for timely deployment once available. 6. Incident Response Preparedness: Develop and test response plans for potential DoS incidents affecting OT systems to minimize downtime and operational impact. 7. Device Hardening: Disable or restrict unnecessary services on WAGO devices if possible, reducing the attack surface. 8. Physical Security: Ensure physical access to WAGO devices is controlled to prevent local exploitation or tampering.