CVE-2025-40765 is a critical security vulnerability identified in Siemens TeleControl Server Basic version 3.1.2.2, affecting all versions from 3.1.2.2 up to but not including 3.1.2.3. The vulnerability is classified under CWE-306, which refers to missing authentication for a critical function. Specifically, the affected TeleControl Server Basic application fails to enforce authentication on certain sensitive operations, allowing an unauthenticated remote attacker to access password hashes of users. With these hashes, attackers can potentially authenticate themselves and perform unauthorized operations on the database service, compromising the system's confidentiality, integrity, and availability. The vulnerability is remotely exploitable without any privileges or user interaction, as indicated by the CVSS vector (AV:N/AC:L/PR:N/UI:N). The CVSS score of 9.8 reflects the critical severity due to the high impact on confidentiality (C:H), integrity (I:H), and availability (A:H). Siemens TeleControl Server Basic is widely used in industrial control systems (ICS) and critical infrastructure sectors for remote monitoring and control. The lack of authentication on critical functions exposes these sensitive environments to potential full compromise. Although no public exploits have been reported yet, the vulnerability's nature and severity make it a prime target for attackers aiming to disrupt industrial operations or steal sensitive credentials. The vulnerability was reserved in April 2025 and published in October 2025, with no patch currently available, increasing the urgency for mitigation measures.

The impact of CVE-2025-40765 on European organizations is substantial, particularly for those operating in critical infrastructure sectors such as energy, manufacturing, transportation, and utilities, where Siemens TeleControl Server Basic is commonly deployed. Exploitation allows attackers to bypass authentication entirely, obtain password hashes, and gain unauthorized access to critical control systems. This can lead to unauthorized manipulation of industrial processes, data theft, operational disruption, and potentially physical damage to infrastructure. The compromise of confidentiality, integrity, and availability can result in severe operational downtime, financial losses, regulatory penalties, and damage to national security. Given the critical role of industrial control systems in Europe’s economy and infrastructure, the vulnerability poses a high risk to business continuity and public safety. Additionally, the ease of exploitation without authentication or user interaction increases the likelihood of attacks, including from nation-state actors or cybercriminal groups targeting European critical infrastructure.

1. Immediate network segmentation and access control: Restrict network access to the TeleControl Server Basic service to trusted management networks only, using firewalls and network segmentation to limit exposure. 2. Monitor and log access: Implement enhanced monitoring of network traffic and system logs for unusual access patterns or attempts to interact with the vulnerable service. 3. Credential management: Since password hashes can be exposed, enforce immediate password resets for all users of the affected system and review authentication policies. 4. Apply vendor patches promptly: Although no patch is currently available, stay in close contact with Siemens for updates and apply security patches as soon as they are released. 5. Implement multi-factor authentication (MFA) where possible on related systems to reduce the risk of credential misuse. 6. Conduct vulnerability scanning and penetration testing focused on TeleControl Server Basic deployments to identify exposure. 7. Develop and test incident response plans specific to ICS compromise scenarios to ensure rapid containment and recovery. 8. Consider deploying intrusion detection/prevention systems (IDS/IPS) tuned to detect exploitation attempts targeting this vulnerability.