CVE-2025-40938 identifies a critical security vulnerability in Siemens SIMATIC CN 4100 devices, specifically in all versions prior to 4.0.1. The root cause is the presence of hard-coded credentials embedded within the device firmware, classified under CWE-798. These credentials are static and cannot be changed by the user, allowing attackers who gain network access to the device to authenticate without authorization. The vulnerability affects the confidentiality, integrity, and availability of the device, as attackers can extract sensitive information, manipulate device operations, or disrupt services. The CVSS v3.1 score of 8.1 reflects a high severity, with an attack vector of network (AV:N), high attack complexity (AC:H), no privileges required (PR:N), and no user interaction (UI:N). The scope is unchanged (S:U), but the impact on confidentiality, integrity, and availability is high (C:H/I:H/A:H). No public exploits have been reported yet, but the vulnerability's nature makes it a prime target for attackers aiming to compromise industrial control systems. Siemens has not yet released a patch, but upgrading to version 4.0.1 or later is recommended once available. The vulnerability is particularly concerning for industrial environments where SIMATIC CN 4100 devices are deployed, as unauthorized access could lead to operational disruptions or safety hazards.

For European organizations, especially those in manufacturing, energy, and critical infrastructure sectors, this vulnerability poses a significant threat. Exploitation could lead to unauthorized access to sensitive operational data, manipulation of control commands, and potential disruption of industrial processes. This could result in production downtime, safety incidents, financial losses, and damage to reputation. Given Siemens' strong presence in Europe and the widespread use of SIMATIC CN 4100 in industrial automation, the risk is amplified. Additionally, attackers could leverage this vulnerability as a foothold for lateral movement within industrial networks, escalating the impact. The high confidentiality, integrity, and availability impacts mean that both data theft and operational sabotage are plausible outcomes. Regulatory compliance issues may also arise if affected organizations fail to address the vulnerability promptly.

1. Upgrade SIMATIC CN 4100 devices to firmware version 4.0.1 or later as soon as Siemens releases the patch to eliminate hard-coded credentials. 2. Implement strict network segmentation to isolate SIMATIC CN 4100 devices from general IT networks and restrict access to trusted management stations only. 3. Employ network-level access controls such as firewalls and VPNs to limit exposure of these devices to untrusted networks. 4. Monitor network traffic for unusual authentication attempts or access patterns targeting SIMATIC CN 4100 devices. 5. Conduct regular security audits and vulnerability scans focusing on industrial control systems to detect potential exploitation attempts. 6. Educate operational technology (OT) personnel about the risks of hard-coded credentials and the importance of applying security updates promptly. 7. Consider deploying intrusion detection systems tailored for industrial protocols used by SIMATIC CN 4100 to detect anomalous behavior. 8. Maintain an incident response plan specific to industrial control system compromises to ensure rapid containment and recovery.