CVE-2025-40773 is a vulnerability classified under CWE-639 (Authorization Bypass Through User-Controlled Key) affecting Siemens SiPass integrated server applications in all versions prior to 3.0. The core issue lies in broken access control mechanisms where the server fails to adequately verify authorization for certain API requests. This allows an attacker with low privileges (PR:L) and access from an adjacent network (AV:A) to bypass intended authorization restrictions and manipulate data belonging to other users. The vulnerability does not require user interaction (UI:N) and the scope remains unchanged (S:U), meaning the attacker’s privileges do not escalate beyond their initial context but can affect other users’ data integrity. The CVSS 3.1 base score is 3.5, indicating a low severity primarily due to the limited impact on confidentiality and availability, and the requirement for some level of privileges. No public exploits or patches have been reported at the time of publication. The vulnerability is significant in environments where SiPass integrated is used for access control and identity management, as unauthorized data manipulation could undermine operational integrity and trust in security controls. Siemens recommends upgrading to version 3.0 or later where this issue is resolved.

For European organizations, especially those in critical infrastructure sectors such as energy, transportation, and manufacturing that rely on Siemens SiPass integrated for physical access control, this vulnerability could allow attackers to manipulate user data, potentially disrupting access permissions or audit logs. While confidentiality and availability are not directly impacted, integrity violations could lead to unauthorized access or denial of legitimate access if data is altered maliciously. This could have downstream effects on operational security and compliance with regulations like GDPR if access control data is compromised. The low CVSS score suggests limited risk, but the potential for insider threats or lateral movement within networks increases the importance of addressing this vulnerability promptly. Organizations with extensive Siemens deployments should assess their exposure and prioritize remediation to maintain trust in their access control systems.

To mitigate CVE-2025-40773, European organizations should: 1) Upgrade Siemens SiPass integrated to version 3.0 or later where the vulnerability is fixed. 2) Implement strict network segmentation to limit access to SiPass integrated servers only to trusted and necessary hosts, reducing the attack surface from adjacent networks. 3) Enforce the principle of least privilege for all users interacting with the SiPass API to minimize the potential for exploitation by low-privilege attackers. 4) Monitor API usage logs for unusual or unauthorized requests that could indicate attempts to exploit broken access controls. 5) Conduct regular security audits and penetration tests focusing on access control mechanisms within SiPass integrated deployments. 6) Apply compensating controls such as multi-factor authentication for administrative access to reduce risk from compromised credentials. 7) Stay informed on Siemens security advisories for any patches or updates related to this vulnerability.