CVE-2025-40818 is a security vulnerability identified in Siemens SINEMA Remote Connect Server versions earlier than 3.2 SP4. The issue arises from incorrect permission assignments (CWE-732) on critical resources, specifically private SSL/TLS keys stored on the server. These keys are not adequately protected, allowing any user with access to the server's file system to read them. Since these private keys are used for server authentication and establishing secure communications, their exposure can enable an attacker with authenticated local access to impersonate the server. This impersonation can facilitate man-in-the-middle attacks, decrypt encrypted traffic, or gain unauthorized access to services that trust the compromised certificates. The vulnerability requires the attacker to have local privileges on the server, which limits remote exploitation but does not eliminate risk if an attacker gains such access through other means. The CVSS 3.1 base score is 3.3, reflecting low severity due to limited impact on integrity and availability and the need for local privileges. However, the confidentiality impact is significant because private keys are sensitive assets. Siemens has acknowledged the vulnerability and addressed it in version 3.2 SP4, but no public patch links are currently provided. No known exploits have been reported in the wild, but the vulnerability remains a concern for environments where server access controls are weak or compromised.

For European organizations, particularly those in industrial automation, critical infrastructure, and manufacturing sectors that rely on Siemens SINEMA Remote Connect Server for secure remote access, this vulnerability poses a confidentiality risk. Exposure of private SSL/TLS keys could allow attackers who have gained local access to the server to impersonate the server, intercept or decrypt sensitive communications, and potentially access other trusted services. This could lead to unauthorized data disclosure and undermine trust in secure communications. While the vulnerability does not directly affect system integrity or availability, the ability to perform man-in-the-middle attacks could facilitate further exploitation or lateral movement within networks. The risk is heightened in environments where server access controls are insufficient or where attackers have already compromised user credentials or systems. Given Siemens' strong presence in European industrial sectors, the impact could affect critical operations and supply chains if exploited.

Organizations should immediately verify the version of SINEMA Remote Connect Server in use and plan to upgrade to version 3.2 SP4 or later, where the vulnerability is addressed. Until the upgrade is applied, strict access controls must be enforced on the server file system to restrict access to private SSL/TLS key files only to necessary system processes and administrators. Implement file system permissions audits and monitoring to detect unauthorized access attempts. Employ network segmentation and strong authentication mechanisms to limit server access to trusted personnel and systems. Regularly review and harden server configurations to minimize the risk of privilege escalation or unauthorized local access. Additionally, consider deploying host-based intrusion detection systems to alert on suspicious file access patterns. Finally, maintain up-to-date backups and incident response plans tailored to potential credential compromise scenarios.