CVE-2025-54660 is a vulnerability identified in Fortinet's FortiClientWindows VPN client software, specifically affecting versions 7.0.0, 7.2.0 through 7.2.10, and 7.4.0 through 7.4.3. The root cause is the presence of active debug code within the application that can be leveraged by a local attacker to execute the application step-by-step, effectively enabling them to retrieve saved VPN user passwords stored by the client. This vulnerability requires the attacker to have local access with limited privileges (PR:L) but does not require user interaction (UI:N). The attack vector is local (AV:L), meaning remote exploitation is not feasible without prior access. The vulnerability impacts confidentiality (C:H) by exposing sensitive credentials but does not affect integrity or availability. The CVSS v3.1 base score is 4.9, reflecting medium severity. The vulnerability is currently published and assigned by Fortinet, with no known exploits in the wild. The lack of patch links suggests that remediation may require vendor updates or configuration changes. This vulnerability could allow an attacker who has gained local access to a system to escalate their privileges or move laterally by leveraging exposed VPN credentials, posing a risk to organizational network security.

For European organizations, the exposure of VPN user passwords through this vulnerability could lead to unauthorized access to corporate networks, especially where FortiClientWindows is widely deployed for remote access. This could facilitate lateral movement within networks, data exfiltration, or further compromise of sensitive systems. Confidentiality of user credentials is directly impacted, increasing the risk of credential theft and misuse. Organizations in sectors with high VPN usage, such as finance, government, healthcare, and critical infrastructure, face heightened risks. The requirement for local access limits the attack surface but insider threats or attackers who have already compromised endpoint devices could exploit this vulnerability. The absence of known exploits reduces immediate risk but does not eliminate the threat, especially as attackers may develop exploits once the vulnerability is public. Overall, this vulnerability could undermine trust in VPN security and complicate incident response efforts in European enterprises.

To mitigate CVE-2025-54660, European organizations should first verify if they are running affected FortiClientWindows versions (7.0.0, 7.2.0-7.2.10, 7.4.0-7.4.3). They should monitor Fortinet’s advisories for official patches or updates addressing this vulnerability and apply them promptly once available. In the interim, restrict local access to systems running FortiClientWindows to trusted users only and enforce strict endpoint security controls, including application whitelisting and privilege management, to prevent unauthorized local execution or debugging of the VPN client. Employ endpoint detection and response (EDR) solutions to detect suspicious debugging or process manipulation activities. Additionally, enforce strong multi-factor authentication (MFA) for VPN access to reduce the impact of credential exposure. Regularly audit and rotate VPN credentials and consider using hardware-based credential storage or secure vaults to minimize password exposure. Educate users about the risks of local privilege escalation and enforce least privilege principles to limit potential attacker capabilities.