CVE-2025-54660 is a vulnerability discovered in Fortinet's FortiClientWindows VPN client software, specifically versions 7.0.0, 7.2.0 through 7.2.10, and 7.4.0 through 7.4.3. The flaw stems from active debug code left in the application binaries, which allows a local attacker with low privileges to run the FortiClient application in a step-by-step debugging mode. This debugging capability enables the attacker to intercept and retrieve sensitive information, notably the saved VPN user passwords stored by the client. The vulnerability requires local access and privileges (PR:L), but no user interaction (UI:N) is needed to exploit it. The CVSS v3.1 score is 4.9 (medium), reflecting the moderate risk posed by the vulnerability. The impact is primarily on confidentiality (C:H), as the attacker can disclose VPN credentials, potentially leading to unauthorized network access if those credentials are reused or provide lateral movement opportunities. There is no impact on integrity or availability. The vulnerability has been publicly disclosed but no known exploits have been reported in the wild to date. The presence of debug code in production software indicates a development oversight, and the vulnerability highlights the importance of secure software release practices. Fortinet has not yet published patches or mitigation instructions at the time of this report, so organizations must rely on compensating controls until updates are available.

For European organizations, the exposure of VPN user passwords can have significant security implications. VPN credentials often provide access to internal corporate networks, sensitive data, and critical infrastructure. If an attacker gains local access to an endpoint (e.g., through physical access, compromised user accounts, or insider threats), they could extract these credentials and use them to bypass perimeter defenses, escalate privileges, or move laterally within the network. This risk is heightened in sectors with stringent data protection requirements such as finance, healthcare, and government agencies. Confidentiality breaches could lead to data leaks, regulatory penalties under GDPR, and reputational damage. However, the requirement for local privileges limits remote exploitation, reducing the attack surface somewhat. Organizations with remote or hybrid workforces relying heavily on FortiClient for VPN access are particularly vulnerable if endpoint security is weak. The lack of known exploits in the wild suggests a window of opportunity for defenders to implement mitigations before active attacks emerge.

1. Monitor Fortinet’s official channels closely for patches addressing CVE-2025-54660 and apply them promptly once released. 2. Restrict local user privileges on endpoints to the minimum necessary to reduce the risk of local exploitation. 3. Implement endpoint security controls such as application whitelisting, anti-debugging protections, and host-based intrusion detection to detect or prevent debugging attempts. 4. Enforce strong physical security policies to prevent unauthorized local access to devices. 5. Educate users about the risks of local credential exposure and encourage the use of multifactor authentication (MFA) for VPN access to mitigate credential theft impact. 6. Regularly audit and monitor VPN access logs for unusual login patterns that could indicate compromised credentials. 7. Consider using credential vaulting or secure storage mechanisms that do not rely on storing plaintext or easily extractable passwords on endpoints. 8. Isolate critical systems and sensitive data to limit lateral movement if credentials are compromised. 9. Employ network segmentation and zero-trust principles to reduce the impact of credential disclosure. 10. Conduct regular security assessments and penetration tests focusing on endpoint security and VPN client configurations.