CVE-2025-40940 identifies a vulnerability in Siemens SIMATIC CN 4100 devices, specifically in versions prior to 4.0.1, related to inconsistent behavior in the Simple Network Management Protocol (SNMP) implementation. The affected devices exhibit unexpected service availability and unreliable configuration handling across different SNMP protocol versions, which can lead to exposure of sensitive information to unauthorized actors. The root cause is linked to improper management of SNMP services and configurations, allowing attackers with high privileges to bypass expected access controls and retrieve confidential data. The vulnerability is classified under CWE-200 (Exposure of Sensitive Information), indicating that sensitive data could be disclosed without proper authorization. The CVSS v3.1 score is 4.9 (medium severity), reflecting that the attack vector is network-based (AV:N), requires low attack complexity (AC:L), but demands high privileges (PR:H) and no user interaction (UI:N). The impact is limited to confidentiality (C:H), with no effect on integrity or availability. No public exploits have been reported yet, but the vulnerability poses a risk to industrial control systems relying on SIMATIC CN 4100 for network communication. Siemens has reserved the CVE and published the advisory, but no patch links are currently available, indicating that remediation may be pending or forthcoming.

For European organizations, particularly those operating industrial control systems (ICS) and critical infrastructure, this vulnerability presents a risk of sensitive data exposure. Siemens SIMATIC CN 4100 devices are commonly used in manufacturing, energy, and transportation sectors across Europe. Unauthorized disclosure of configuration details or operational data could facilitate further targeted attacks, espionage, or disruption planning. Although exploitation requires high privileges, insider threats or lateral movement by attackers could leverage this vulnerability to escalate access or gather intelligence. The confidentiality breach could undermine operational security, regulatory compliance (e.g., NIS Directive), and trust in industrial automation environments. Given the strategic importance of Siemens products in Europe’s industrial landscape, the vulnerability could impact national critical infrastructure resilience and economic stability if exploited.

Organizations should prioritize upgrading SIMATIC CN 4100 devices to version 4.0.1 or later once patches are available from Siemens. Until then, network segmentation should be enforced to restrict SNMP access strictly to trusted management networks and authorized personnel. Implement strong authentication and access controls for SNMP management interfaces, including the use of SNMPv3 with encryption and authentication where supported. Monitor network traffic for anomalous SNMP requests or unexpected service availability. Conduct regular audits of device configurations to detect inconsistencies or unauthorized changes. Employ intrusion detection systems tailored for ICS environments to identify potential reconnaissance or exploitation attempts. Additionally, establish incident response plans specific to industrial control system vulnerabilities and ensure staff are trained to recognize and respond to such threats.