CVE-2025-40937 is a command injection vulnerability classified under CWE-77 affecting Siemens SIMATIC CN 4100 devices running versions earlier than V4.0.1. The root cause is improper neutralization of special elements in input parameters submitted via the device's REST API. Specifically, the application fails to properly validate or sanitize unexpected arguments, which an authenticated attacker can exploit to inject and execute arbitrary commands on the underlying system. The vulnerability requires the attacker to have limited privileges authentication, but no user interaction is needed. The CVSS v3.1 score is 8.3, indicating high severity, with attack vector network (AV:N), low attack complexity (AC:L), privileges required low (PR:L), no user interaction (UI:N), unchanged scope (S:U), and high impact on confidentiality and integrity (C:H/I:H) with low availability impact (A:L). Successful exploitation could allow attackers to compromise sensitive data, alter system configurations, or disrupt operations by executing unauthorized commands. The vulnerability affects all versions of SIMATIC CN 4100 prior to V4.0.1, a product widely used in industrial automation and control environments. No public exploits or active exploitation have been reported yet, but the nature of the vulnerability and the criticality of affected systems make it a significant risk. Siemens has not yet published patches but the vulnerability is officially reserved and published in the CVE database.

For European organizations, especially those in manufacturing, energy, and critical infrastructure sectors relying on Siemens SIMATIC CN 4100 devices, this vulnerability poses a substantial risk. Exploitation could lead to unauthorized command execution, potentially resulting in data breaches, manipulation of industrial processes, or partial service disruptions. The high confidentiality and integrity impact could compromise sensitive operational data and control logic, undermining trust and safety. Although availability impact is rated low, targeted attacks could still cause operational delays or safety incidents. Given the widespread use of Siemens industrial products in Europe, the vulnerability could affect supply chains and critical infrastructure resilience. Attackers with limited privileges could escalate their control, making this a significant threat vector for espionage, sabotage, or ransomware delivery within industrial environments.

1. Apply Siemens' official patch for SIMATIC CN 4100 as soon as it becomes available to address the input validation flaw. 2. Until patches are released, restrict access to the REST API to trusted networks and authenticated users only, employing network segmentation and firewall rules. 3. Implement strict input validation and sanitization controls on all interfaces interacting with SIMATIC CN 4100 devices, if possible via proxy or gateway solutions. 4. Monitor device logs and network traffic for unusual commands or access patterns indicative of exploitation attempts. 5. Enforce the principle of least privilege for all accounts accessing the device to limit potential damage from compromised credentials. 6. Conduct regular security audits and vulnerability assessments on industrial control systems to identify and remediate similar issues proactively. 7. Train operational technology (OT) personnel on recognizing and responding to signs of command injection attacks and unauthorized access.