CVE-2025-11743 is a vulnerability classified under CWE-1284, indicating improper validation of a specified quantity in input. It affects Rockwell Automation CompactLogix® 5370 programmable logic controllers (PLCs), widely used in industrial automation. The vulnerability is triggered when a specially crafted, malformed CIP (Common Industrial Protocol) forward open message is sent to the device. This malformed message causes the device to enter a major nonrecoverable fault state, effectively resulting in a denial-of-service (DoS) condition. Recovery from this fault requires a manual restart of the device, causing downtime and potential disruption to industrial processes. The vulnerability affects multiple firmware versions: 34.013 and prior, 35.012 and prior, and 36.011. The CVSS v4.0 score is 7.1, reflecting high severity, with an attack vector of adjacent network (AV:A), low attack complexity (AC:L), no privileges required (PR:N), no user interaction (UI:N), and a high impact on availability (VA:H). The flaw does not impact confidentiality or integrity but severely impacts availability, which is critical in industrial environments. No known exploits have been reported in the wild yet, but the vulnerability's characteristics make it a plausible target for attackers aiming to disrupt industrial operations. The CIP protocol is commonly used in industrial control systems, and improper input validation in this protocol can have serious consequences. The lack of authentication or user interaction requirements means an attacker with network access to the affected device can exploit the vulnerability remotely. This elevates the risk in environments where network segmentation or access controls are insufficient. The vulnerability highlights the importance of validating protocol messages rigorously in industrial control systems to prevent denial-of-service conditions that can halt critical infrastructure operations.

For European organizations, especially those in manufacturing, energy, and critical infrastructure sectors, this vulnerability poses a significant risk of operational disruption. CompactLogix® 5370 controllers are integral to automation processes, and a forced restart due to a nonrecoverable fault can lead to production downtime, safety risks, and financial losses. The denial-of-service condition could interrupt supply chains and industrial workflows, impacting business continuity. Since the vulnerability can be exploited remotely without authentication, attackers could leverage it to cause targeted outages or as part of a broader attack campaign. The impact is particularly severe in environments where high availability and real-time control are essential, such as power plants, water treatment facilities, and manufacturing lines. Additionally, recovery requires manual intervention, which may delay restoration of normal operations. The lack of known exploits in the wild currently reduces immediate risk but does not eliminate the threat, especially as threat actors often develop exploits after public disclosure. European organizations must consider this vulnerability in their risk assessments and incident response planning to mitigate potential impacts on critical infrastructure and industrial automation.

1. Apply firmware updates and patches provided by Rockwell Automation as soon as they become available to address CVE-2025-11743. 2. Implement strict network segmentation to isolate CompactLogix® 5370 controllers from general IT networks and limit access to trusted management systems only. 3. Use firewalls and intrusion detection/prevention systems (IDS/IPS) configured to monitor and filter CIP protocol traffic, blocking malformed or unexpected messages. 4. Restrict network access to the affected devices by enforcing strong access control policies, including limiting connections to known IP addresses and using VPNs or secure tunnels for remote access. 5. Conduct regular network traffic analysis to detect anomalies indicative of malformed CIP messages or scanning activity targeting industrial control protocols. 6. Develop and test incident response procedures for denial-of-service events affecting industrial controllers to minimize downtime and ensure rapid recovery. 7. Educate operational technology (OT) personnel about this vulnerability and the importance of monitoring and securing CIP communications. 8. Consider deploying application-layer gateways or protocol-aware security devices that can validate CIP message integrity and reject malformed packets before they reach the controller. 9. Maintain an inventory of affected devices and firmware versions to prioritize remediation efforts effectively. 10. Collaborate with vendors and industry groups to stay informed about updates, patches, and emerging threats related to industrial control systems.