CVE-2025-40817 identifies a missing authentication vulnerability (CWE-306) in multiple Siemens LOGO! PLC models, including LOGO! 12/24RCE, 230RCE, and 24CE variants, as well as their SIPLUS versions. These devices are widely used in industrial automation for controlling machinery and processes. The vulnerability stems from the devices not performing necessary authentication checks when receiving commands to change their internal system time. An unauthenticated remote attacker with network access adjacent to the device can exploit this flaw to alter the device's clock. Changing the device time can lead to incorrect operation of time-dependent logic, potentially causing process errors, misalignment in event logging, or triggering unintended automation sequences. The CVSS v3.1 score is 6.5 (medium severity), reflecting that the attack vector is adjacent network (AV:A), attack complexity is low (AC:L), no privileges or user interaction are required, and the impact is limited to integrity (I:H) without affecting confidentiality or availability. No patches are currently listed, and no exploits are known in the wild. The vulnerability affects all versions of the listed Siemens LOGO! models, indicating a systemic issue in the authentication design for time-setting functions. This flaw could be leveraged in targeted attacks against industrial control systems (ICS) to disrupt operations or cause safety incidents by manipulating timing-dependent controls.

For European organizations, especially those in manufacturing, utilities, and critical infrastructure sectors that rely on Siemens LOGO! PLCs for automation, this vulnerability poses a risk to operational integrity. Altering device time can disrupt process control logic, cause incorrect sequencing of operations, and lead to inaccurate event logging, complicating incident response and forensic analysis. While the vulnerability does not directly compromise confidentiality or availability, the integrity impact can result in production downtime, safety hazards, or equipment damage if automation behaves unpredictably. Given the widespread use of Siemens automation products in Europe, particularly in Germany, France, Italy, and the UK, the potential for targeted disruption exists. Attackers with network access could exploit this flaw to cause subtle but impactful process deviations, potentially affecting supply chains and industrial output. The absence of authentication also increases the risk from insider threats or lateral movement within industrial networks.

1. Implement strict network segmentation to isolate Siemens LOGO! devices from general IT networks and restrict access to trusted management stations only. 2. Employ firewall rules and access control lists (ACLs) to limit network traffic to the PLCs, allowing only authorized protocols and sources. 3. Monitor device logs and network traffic for unusual time change commands or anomalies in device behavior. 4. Use secure remote access solutions with multi-factor authentication for any legitimate remote management. 5. Regularly audit and update device firmware and software; apply vendor patches promptly once released. 6. Establish incident response procedures specific to industrial control systems to quickly identify and remediate time manipulation attempts. 7. Consider deploying intrusion detection systems (IDS) tailored for ICS environments to detect unauthorized commands. 8. Train operational technology (OT) personnel on this vulnerability and best practices for securing PLCs. 9. If possible, configure devices to alert on time changes or restrict time-setting commands to authenticated sessions. 10. Collaborate with Siemens support and stay informed on updates or advisories related to this vulnerability.