CVE-2025-41738 is a vulnerability classified under CWE-843 (Access of Resource Using Incompatible Type, commonly known as type confusion) found in the CODESYS Control Runtime Environment (RTE) for the SL platform, specifically version 3.5.18.0. The vulnerability resides in the visualisation server component of the runtime system, which is responsible for rendering and managing human-machine interface (HMI) visualizations in industrial automation setups. An unauthenticated remote attacker can exploit this flaw by sending specially crafted network requests that cause the server to dereference pointers of an incorrect type. This type confusion can lead to memory corruption, resulting in a denial-of-service (DoS) condition by crashing the visualisation server or causing it to become unresponsive. The vulnerability has a CVSS v3.1 base score of 7.5, indicating high severity, with an attack vector of network (AV:N), no privileges required (PR:N), no user interaction (UI:N), and impact limited to availability (A:H) without affecting confidentiality or integrity. No known exploits have been reported in the wild as of the publication date, but the ease of remote exploitation without authentication makes this a critical concern for industrial environments that rely on CODESYS for control and monitoring. The lack of available patches at the time of disclosure necessitates immediate risk mitigation through network segmentation and monitoring until vendor fixes are released.

The primary impact of CVE-2025-41738 is a denial-of-service condition affecting the availability of the CODESYS Control RTE visualisation server. For European organizations, particularly those in manufacturing, energy, and critical infrastructure sectors that utilize CODESYS for industrial automation, this can translate into operational downtime, loss of control visibility, and potential disruption of industrial processes. Such outages can have cascading effects on production lines, safety systems, and supply chains. Since the vulnerability requires no authentication and can be triggered remotely, attackers could exploit it to cause widespread disruption. The loss of availability in industrial control systems can also increase safety risks and lead to financial losses. Furthermore, the inability to visualize system states may delay incident response and recovery efforts. The impact is heightened in countries with dense industrial automation deployments and critical infrastructure relying on CODESYS, making timely mitigation essential to maintain operational continuity and safety.

1. Apply patches or updates from CODESYS as soon as they become available to address CVE-2025-41738. 2. Until patches are released, restrict network access to the visualisation server component by implementing strict firewall rules and network segmentation to isolate the CODESYS Control RTE from untrusted networks. 3. Employ intrusion detection and prevention systems (IDS/IPS) to monitor and block suspicious traffic targeting the visualisation server ports. 4. Conduct regular network traffic analysis to identify anomalous requests that could indicate exploitation attempts. 5. Limit exposure by disabling unnecessary services and interfaces on the CODESYS runtime environment. 6. Implement robust logging and alerting mechanisms to detect crashes or instability in the visualisation server promptly. 7. Train operational technology (OT) security teams to recognize signs of exploitation and respond swiftly. 8. Review and enforce strict access control policies for remote connections to industrial control systems. These measures go beyond generic advice by focusing on network-level protections and operational monitoring tailored to the industrial context of CODESYS deployments.