CVE-2025-40937 is a command injection vulnerability classified under CWE-77 that affects Siemens SIMATIC CN 4100 devices running versions earlier than 4.0.1. The root cause is improper neutralization of special elements in input parameters processed by the device's REST API. Specifically, the application fails to adequately validate or sanitize input arguments, allowing an authenticated attacker to inject malicious commands. Exploitation requires authentication but no user interaction, and can be performed remotely over the network. Successful exploitation enables the attacker to execute arbitrary code with limited privileges on the affected device, potentially leading to unauthorized access, data manipulation, or further lateral movement within industrial control networks. The vulnerability has a CVSS v3.1 base score of 8.3, indicating high severity, with metrics AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:L, meaning it is remotely exploitable with low attack complexity, requires low privileges, no user interaction, and impacts confidentiality and integrity significantly, with limited availability impact. No public exploits are currently known, but the vulnerability is published and should be addressed promptly. Siemens SIMATIC CN 4100 is widely used in industrial automation environments, making this vulnerability particularly critical for operational technology (OT) security.

For European organizations, especially those in manufacturing, energy, and critical infrastructure sectors relying on Siemens SIMATIC CN 4100, this vulnerability poses a significant risk. Exploitation could lead to unauthorized command execution, resulting in data breaches, manipulation of industrial processes, or disruption of operations. The confidentiality and integrity of sensitive operational data could be compromised, potentially affecting product quality, safety, and compliance with regulatory requirements such as NIS2. Although availability impact is rated low, any unauthorized code execution in OT environments can have cascading effects on system stability and safety. The vulnerability's remote exploitability increases the attack surface, particularly if devices are exposed to less secure networks or insufficiently segmented environments. European organizations with interconnected IT and OT networks may face increased risk of lateral movement by attackers leveraging this flaw. The lack of known exploits currently provides a window for proactive mitigation before widespread exploitation occurs.

1. Immediately upgrade all Siemens SIMATIC CN 4100 devices to version 4.0.1 or later, where the vulnerability is fixed. 2. Implement strict input validation and sanitization on all REST API endpoints to prevent injection of malicious commands. 3. Enforce strong authentication and access control policies to limit access to the REST API only to trusted and authorized users. 4. Segment industrial control networks from corporate IT networks and restrict network access to SIMATIC CN 4100 devices using firewalls and network access control lists. 5. Monitor network traffic and device logs for unusual command execution patterns or unauthorized access attempts. 6. Conduct regular vulnerability assessments and penetration testing focused on OT environments to detect similar weaknesses. 7. Develop and test incident response plans specific to OT environments to quickly contain and remediate any exploitation attempts. 8. Collaborate with Siemens support and subscribe to their security advisories for timely updates and patches.