CVE-2025-46373 is a heap-based buffer overflow vulnerability identified in Fortinet's FortiClientWindows software, specifically affecting versions 7.2.0 through 7.2.8 and 7.4.0 through 7.4.3. The flaw resides in the "fortips_74.sys" driver, which handles IPSec VPN functionality. An authenticated local user with IPSec privileges can exploit this vulnerability by triggering a heap overflow condition, potentially leading to arbitrary code execution with elevated privileges. Successful exploitation requires bypassing Windows heap integrity protections, such as heap cookies and safe unlinking mechanisms, which adds complexity but does not make exploitation impossible. The vulnerability affects confidentiality, integrity, and availability by allowing an attacker to execute unauthorized commands or code, potentially leading to full system compromise. The CVSS v3.1 score of 7.1 reflects a high severity level, with attack vector local (AV:L), attack complexity high (AC:H), privileges required low (PR:L), no user interaction (UI:N), and scope changed (S:C). No public exploits are currently known, but the vulnerability is published and should be considered a significant risk for organizations using affected FortiClientWindows versions. Fortinet FortiClient is widely deployed in enterprise environments for VPN and endpoint security, making this vulnerability particularly relevant for organizations relying on IPSec VPNs for secure remote access.

For European organizations, this vulnerability poses a substantial risk, especially those using FortiClientWindows for IPSec VPN connectivity. Exploitation could allow a local authenticated attacker to escalate privileges and execute arbitrary code, potentially leading to full system compromise. This could result in data breaches, disruption of business operations, and unauthorized access to sensitive networks. Sectors such as finance, government, healthcare, and critical infrastructure that rely heavily on secure VPN connections are particularly vulnerable. The need for local authentication limits remote exploitation but insider threats or compromised endpoints could leverage this flaw. Additionally, the ability to alter system integrity and availability could disrupt critical services. The absence of known exploits in the wild currently reduces immediate risk but does not eliminate it, especially as threat actors may develop exploits post-disclosure. European organizations must prioritize patching and monitoring to mitigate potential impacts.

1. Apply official patches from Fortinet immediately once they become available for affected FortiClientWindows versions. 2. Restrict local IPSec user privileges to the minimum necessary, limiting the number of users who can authenticate locally with IPSec capabilities. 3. Implement strict endpoint security controls to detect and prevent unauthorized local access or privilege escalation attempts. 4. Monitor system logs and security telemetry for unusual activity related to the "fortips_74.sys" driver or local privilege escalations. 5. Employ application whitelisting and behavior-based detection to identify anomalous command execution. 6. Conduct regular security audits and vulnerability assessments focusing on VPN client software and local user permissions. 7. Educate users about the risks of local privilege misuse and enforce strong authentication policies. 8. Consider network segmentation to limit the impact of a compromised endpoint. 9. Use advanced endpoint detection and response (EDR) solutions capable of detecting heap overflow exploitation techniques. 10. Maintain up-to-date backups and incident response plans to quickly recover from potential compromises.