CVE-2025-58903 is a vulnerability identified in Fortinet's FortiOS operating system, specifically affecting versions 7.6.0 through 7.6.3 and versions prior to 7.4.8. The flaw is categorized as an Unchecked Return Value vulnerability (CWE-252) that leads to a null pointer dereference within the HTTP daemon component of FortiOS. This occurs when an authenticated user sends a specially crafted API request, which the system fails to properly validate or handle, causing the HTTP daemon process to crash. The crash results in a denial of service (DoS) condition, temporarily disrupting management and potentially other services relying on the HTTP daemon. The vulnerability requires authenticated access, meaning an attacker must already have valid credentials or access to an authenticated session to exploit it. No user interaction beyond the crafted request is necessary. The CVSS v3.1 base score is 2.5, reflecting low severity due to the limited impact scope—no confidentiality or integrity loss, only availability impact. The exploitability is rated as low since it requires authentication and specialized requests. No public exploits or active exploitation in the wild have been reported as of the publication date. FortiOS is widely used in enterprise and service provider environments for firewalling, VPN, and network security management, making this vulnerability relevant for organizations relying on Fortinet products for perimeter defense and secure remote access.

For European organizations, the primary impact of CVE-2025-58903 is the potential for temporary denial of service affecting network security management and monitoring capabilities. A crash of the HTTP daemon could disrupt administrative access to FortiOS devices, delaying incident response or configuration changes. This could indirectly affect network availability and security posture if remediation or reboots are delayed. However, since the vulnerability does not allow privilege escalation, data leakage, or persistent compromise, the direct risk to confidentiality and integrity is minimal. Organizations with high dependency on Fortinet FortiOS for critical infrastructure, such as telecommunications, finance, and government networks, may experience operational disruptions. The requirement for authenticated access limits exploitation to insiders or attackers who have already compromised credentials, reducing the likelihood of widespread attacks. Nonetheless, denial of service in security devices can have cascading effects on network stability and incident handling.

1. Apply patches or updates from Fortinet as soon as they become available for affected FortiOS versions to remediate the vulnerability. 2. Restrict API and management interface access strictly to trusted administrators and secure management networks using network segmentation and access control lists. 3. Enforce strong authentication mechanisms, such as multi-factor authentication, to reduce the risk of credential compromise. 4. Monitor FortiOS device logs and network traffic for unusual API requests or repeated HTTP daemon crashes indicative of exploitation attempts. 5. Implement redundancy and high availability configurations for FortiOS devices to minimize service disruption in case of daemon crashes. 6. Regularly review and audit user accounts with API access to ensure only necessary privileges are granted. 7. Consider deploying network-based intrusion detection systems to detect anomalous API traffic patterns targeting FortiOS management interfaces.