CVE-2025-40796 identifies an out-of-bounds read vulnerability (CWE-125) in Siemens SIMATIC PCS neo versions 4.1, 5.0, 6.0, and the User Management Component (UMC) versions prior to 2.15.1.3. The vulnerability resides in the integrated UMC, which handles user management functions within the PCS neo platform. An out-of-bounds read occurs when the software reads memory outside the intended buffer boundaries, potentially leading to application crashes or denial of service. This vulnerability can be exploited remotely over the network without requiring authentication or user interaction, making it accessible to unauthenticated attackers. The primary impact is denial of service, as the out-of-bounds read can cause the affected service or system to crash or become unresponsive. There is no indication that confidentiality or integrity of data is compromised. Siemens has published the CVE with a high CVSS v3.1 score of 7.5, reflecting the ease of exploitation (network vector, no privileges required) and the significant impact on availability. No patches or exploits are currently publicly available, but affected organizations should anticipate updates. The vulnerability affects industrial control systems used in process automation, which are critical for manufacturing, utilities, and infrastructure sectors. Exploitation could disrupt industrial operations, causing operational downtime and potential safety risks. The User Management Component is a critical part of the PCS neo platform, and its compromise or failure can impact system stability and access control mechanisms.

For European organizations, the primary impact of CVE-2025-40796 is the potential for denial of service on critical industrial control systems running Siemens SIMATIC PCS neo. This can lead to operational disruptions in manufacturing plants, utilities, and other industrial environments that rely on PCS neo for process automation and control. Downtime in these sectors can result in significant financial losses, safety hazards, and cascading effects on supply chains. Since the vulnerability can be exploited remotely without authentication, attackers could target exposed PCS neo installations from outside the network, increasing the risk of widespread disruption. The lack of confidentiality or integrity impact limits data breach concerns but does not reduce the operational risk. European critical infrastructure operators, especially in energy, chemical, and manufacturing industries, could face increased risk if network defenses are insufficient. The vulnerability also raises concerns about the resilience of industrial control systems against cyberattacks, which is a priority in European cybersecurity regulations and directives such as NIS2. Organizations may also face regulatory and compliance challenges if the vulnerability is exploited and causes service interruptions.

1. Immediately implement network segmentation to isolate SIMATIC PCS neo systems and restrict access to trusted management networks only. 2. Employ strict firewall rules and access control lists to limit inbound traffic to PCS neo interfaces, especially the User Management Component. 3. Monitor network traffic and system logs for unusual or repeated access attempts targeting the UMC or PCS neo components. 4. Prepare for patch deployment by coordinating with Siemens for timely updates once patches are released; prioritize testing and deployment in production environments. 5. Conduct vulnerability scanning and penetration testing focused on PCS neo installations to identify exposure and verify mitigation effectiveness. 6. Implement intrusion detection/prevention systems (IDS/IPS) with signatures or heuristics tuned to detect exploitation attempts of out-of-bounds read vulnerabilities. 7. Train operational technology (OT) security teams on this specific vulnerability and incident response procedures to minimize downtime in case of exploitation. 8. Review and harden user management policies and authentication mechanisms within PCS neo to reduce attack surface. 9. Maintain up-to-date asset inventories to quickly identify affected systems and ensure comprehensive coverage of mitigation efforts.