CVE-2025-40798 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 a CWE-125: Out-of-bounds Read, which occurs when the software reads data outside the boundaries of allocated memory. This flaw can be triggered by an unauthenticated remote attacker without any user interaction, making it particularly dangerous. Exploitation of this vulnerability can lead to a denial of service (DoS) condition, where the affected system becomes unresponsive or crashes, disrupting normal operations. The CVSS v3.1 base score is 7.5, indicating a high severity level, with the vector AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H, meaning the attack can be performed remotely over the network with low attack complexity, no privileges or user interaction required, and results in high impact on availability but no impact on confidentiality or integrity. Siemens SIMATIC PCS neo is a process control system widely used in industrial automation environments, including manufacturing plants, utilities, and critical infrastructure sectors. The UMC component manages user authentication and authorization, making it a critical part of the system's security architecture. The out-of-bounds read vulnerability could be exploited to cause system crashes or instability, potentially halting industrial processes and causing operational disruptions. Currently, there are no known exploits in the wild, and no official patches have been linked yet, emphasizing the need for proactive mitigation and monitoring. Given the nature of the affected product and the vulnerability, this threat is particularly relevant to industrial control systems (ICS) and operational technology (OT) environments where availability is paramount.

For European organizations, especially those operating in industrial sectors such as manufacturing, energy, utilities, and critical infrastructure, this vulnerability poses a significant risk. A denial of service attack on SIMATIC PCS neo systems could lead to operational downtime, production losses, safety risks, and potential regulatory non-compliance. Disruption of process control systems can have cascading effects on supply chains and service delivery. Since the vulnerability can be exploited remotely without authentication, attackers could target exposed systems over the internet or internal networks, increasing the attack surface. The lack of impact on confidentiality and integrity reduces the risk of data breaches but does not diminish the operational impact. European organizations relying on Siemens PCS neo for process automation must consider the potential for service interruptions and the associated financial and reputational damage. Additionally, critical infrastructure operators in Europe are subject to stringent cybersecurity regulations (e.g., NIS Directive), making timely mitigation essential to avoid penalties and ensure resilience.

1. Immediate network-level protections: Restrict access to SIMATIC PCS neo systems and the User Management Component to trusted networks only. Implement network segmentation and firewall rules to limit exposure, especially from the internet. 2. Monitor for unusual activity: Deploy intrusion detection and prevention systems (IDS/IPS) to detect anomalous traffic patterns targeting PCS neo components. 3. Apply vendor updates promptly: Although no patch links are currently provided, organizations should closely monitor Siemens advisories and apply updates or patches as soon as they become available. 4. Implement robust incident response plans: Prepare for potential denial of service incidents by establishing procedures for rapid detection, containment, and recovery to minimize operational impact. 5. Conduct regular vulnerability assessments: Use specialized ICS/OT security tools to scan for vulnerable versions of PCS neo and UMC components within the environment. 6. Harden system configurations: Disable unnecessary services and interfaces on PCS neo systems to reduce attack vectors. 7. Employ network anomaly detection tailored for ICS environments to identify early signs of exploitation attempts. 8. Engage with Siemens support and security teams to receive timely threat intelligence and guidance specific to PCS neo deployments.