CVE-2025-40797 is a high-severity vulnerability identified in Siemens SIMATIC PCS neo versions 4.1 and 5.0, specifically affecting the integrated User Management Component (UMC) in all versions prior to 2.15.1.3. The vulnerability is classified as CWE-125, an out-of-bounds read flaw, which occurs when the software reads data outside the bounds of allocated memory. This flaw can be triggered remotely by an unauthenticated attacker without any user interaction, due to the network-exposed nature of the affected component. Exploiting this vulnerability allows the attacker to cause a denial of service (DoS) condition by crashing or destabilizing the affected system. The CVSS v3.1 base score is 7.5, reflecting a high severity with network attack vector, low attack complexity, no privileges required, and no user interaction needed. The impact is limited to availability, with no direct confidentiality or integrity compromise reported. No known exploits are currently observed in the wild, and Siemens has not yet published patches at the time of this report. The vulnerability affects critical industrial control system (ICS) software used for process control and automation in industrial environments, making it a significant concern for operational technology (OT) security.

For European organizations, particularly those operating in critical infrastructure sectors such as manufacturing, energy, utilities, and chemical processing, this vulnerability poses a substantial risk. Siemens SIMATIC PCS neo is widely deployed across Europe for process control and automation, meaning that exploitation could disrupt industrial operations, leading to production downtime, safety risks, and financial losses. The unauthenticated remote nature of the vulnerability increases the risk of exploitation by external threat actors, including cybercriminals or nation-state actors targeting European industrial facilities. Disruption of availability in these environments can have cascading effects on supply chains and essential services. Although the vulnerability does not directly compromise data confidentiality or integrity, the induced denial of service could halt critical processes and require costly recovery efforts. The lack of known exploits in the wild provides a window for proactive mitigation, but the high severity score and ease of exploitation necessitate urgent attention.

European organizations should immediately conduct an inventory to identify all instances of Siemens SIMATIC PCS neo V4.1, V5.0, and affected UMC versions below 2.15.1.3 within their OT environments. Network segmentation should be enforced to isolate these systems from untrusted networks and limit exposure to potential attackers. Implement strict access controls and monitoring on network segments hosting SIMATIC PCS neo components to detect anomalous activity. Since no official patches are currently available, organizations should engage with Siemens support channels to obtain any interim fixes or recommended workarounds. Applying virtual patching via intrusion prevention systems (IPS) to block malformed packets or suspicious traffic targeting the UMC component may reduce risk. Additionally, organizations should review and harden their incident response plans to quickly address potential denial of service incidents affecting industrial control systems. Regular backups and system redundancy can help minimize operational impact if a DoS event occurs. Finally, maintain close monitoring of Siemens advisories for patch releases and apply updates promptly once available.