CVE-2025-40818 is a security vulnerability identified in Siemens SINEMA Remote Connect Server versions prior to 3.2 SP4. The core issue is an incorrect permission assignment (CWE-732) that results in private SSL/TLS keys stored on the server being accessible to any user with server access. These private keys are critical security assets used to establish secure communications and authenticate the server to clients and other services. Because the keys are not properly protected, an authenticated attacker with local or remote access to the server could read these keys and use them to impersonate the server. This impersonation could facilitate man-in-the-middle (MITM) attacks, allowing interception and decryption of encrypted traffic, or unauthorized access to services that trust the compromised certificates. The vulnerability does not require user interaction and has a CVSS v3.1 base score of 3.3, reflecting low severity primarily due to the requirement for authenticated access and limited confidentiality impact. There is no impact on integrity or availability. No public exploits or active exploitation have been reported. The vulnerability affects all versions of SINEMA Remote Connect Server prior to version 3.2 SP4, and Siemens has not yet published a patch link in the provided data. The vulnerability highlights the importance of proper file permission management for critical cryptographic materials in industrial remote access solutions.

For European organizations, especially 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 risk of credential compromise and unauthorized access. If an attacker gains authenticated access to the server, they could extract private SSL/TLS keys and impersonate the server, potentially intercepting sensitive operational data or disrupting secure communications. This could lead to exposure of confidential information or unauthorized control over remote access sessions. While the vulnerability does not directly affect system integrity or availability, the confidentiality breach could facilitate further attacks or espionage. The risk is heightened in environments where server access controls are weak or where insider threats exist. Given Siemens' strong presence in European industrial sectors, the impact could be significant if exploited, particularly in critical infrastructure such as energy, manufacturing, and transportation.

European organizations should immediately verify their SINEMA Remote Connect Server version and upgrade to version 3.2 SP4 or later once available. Until patched, organizations must enforce strict access controls to limit server access only to trusted administrators and authenticated users with a legitimate need. Implement robust monitoring and logging of server access to detect unauthorized attempts. Review and harden file system permissions on the server to ensure private keys are accessible only by the system processes and authorized administrators. Consider isolating the SINEMA Remote Connect Server in a segmented network zone with limited exposure. Employ multi-factor authentication for all users accessing the server to reduce risk of credential compromise. Regularly audit and rotate cryptographic keys and certificates to limit exposure duration. Finally, maintain up-to-date incident response plans to quickly address any signs of compromise related to this vulnerability.