CVE-2025-46373 is a heap-based buffer overflow vulnerability identified in Fortinet's FortiClientWindows software, specifically versions 7.2.0 through 7.2.8 and 7.4.0 through 7.4.3. The vulnerability resides in the "fortips_74.sys" driver, which is part of the FortiClientWindows suite responsible for IPSec VPN functionality. An authenticated local user with IPSec privileges can exploit this flaw to execute arbitrary code or commands on the affected system. The attack vector requires local access and the ability to authenticate as an IPSec user, which limits remote exploitation but still poses a significant risk in environments where multiple users have local access or where endpoint security is lax. The vulnerability is a heap-based buffer overflow (CWE-122), which means that improper handling of memory buffers can lead to overwriting critical memory areas, enabling code execution. Exploitation also requires bypassing Windows heap integrity protections, which adds complexity but does not eliminate the threat. The CVSS v3.1 base score is 7.1, reflecting high severity due to the potential for complete system compromise (confidentiality, integrity, and availability impacts) and the scope of affected systems. No public exploits are known at this time, but the vulnerability's presence in widely deployed VPN client software makes it a significant concern for organizations relying on FortiClientWindows for secure remote access.

For European organizations, the impact of CVE-2025-46373 can be severe. FortiClientWindows is commonly used to secure remote access via IPSec VPNs, which are critical for business continuity and secure communications. Successful exploitation could allow an authenticated local user to escalate privileges, execute arbitrary code, and potentially gain full control over the endpoint. This could lead to data breaches, lateral movement within corporate networks, disruption of services, and compromise of sensitive information. Organizations with multiple users having local access or shared workstations are particularly vulnerable. The confidentiality, integrity, and availability of corporate data and systems could be compromised, affecting regulatory compliance (e.g., GDPR) and causing reputational damage. The lack of known exploits in the wild currently reduces immediate risk but does not diminish the urgency of remediation due to the high severity and potential for future exploit development.

1. Apply official patches from Fortinet immediately once they are released for the affected FortiClientWindows versions. 2. Until patches are available, restrict local IPSec user privileges to the minimum necessary, limiting the number of users who can authenticate locally with IPSec credentials. 3. Implement strict endpoint security controls, including application whitelisting and behavior monitoring, to detect anomalous local activity indicative of exploitation attempts. 4. Use Windows security features such as heap integrity protections and enable enhanced mitigation experience toolkit (EMET) or Windows Defender Exploit Guard to harden systems against heap-based overflows. 5. Conduct regular audits of local user accounts and permissions to ensure no unauthorized escalation paths exist. 6. Educate IT staff and users about the risks of local privilege misuse and enforce policies to prevent unauthorized local access. 7. Monitor Fortinet and cybersecurity advisories for updates on exploit availability and additional mitigation guidance.