CVE-2024-40591 is a critical privilege escalation vulnerability affecting multiple versions of Fortinet FortiOS, including 7.6.0, 7.4.x, 7.2.x, and versions prior to 7.0.15. The vulnerability arises from incorrect privilege assignment (CWE-266) within the Security Fabric permission model. An authenticated administrator with Security Fabric permissions can exploit this flaw by connecting the targeted FortiGate device to a malicious upstream FortiGate device controlled by the attacker. This connection allows the attacker to escalate their privileges to super-admin level, granting full administrative control over the FortiGate device. The vulnerability can be exploited remotely over the network without requiring user interaction, making it a significant risk for organizations relying on FortiOS for network security. The CVSS 3.1 base score of 8.0 reflects high impact on confidentiality, integrity, and availability, with low attack complexity and partial privileges required. Although no public exploits are currently known, the vulnerability's nature and ease of exploitation make it a critical concern. Fortinet has not yet published patches or mitigation details, so organizations must implement interim controls to limit exposure.

The exploitation of CVE-2024-40591 can have severe consequences for organizations worldwide. An attacker gaining super-admin privileges on a FortiGate device can fully control firewall configurations, security policies, VPNs, and network traffic inspection, potentially leading to unauthorized data access, network disruption, and persistent backdoors. This undermines the confidentiality, integrity, and availability of critical network infrastructure. Organizations relying on FortiGate devices for perimeter defense and internal segmentation are at risk of lateral movement and further compromise. The vulnerability's remote exploitation capability increases the attack surface, especially in environments where multiple administrators have Security Fabric permissions. The impact extends to sectors with high reliance on Fortinet products, including government, finance, healthcare, and telecommunications, where network security is paramount.

1. Immediately restrict Security Fabric permissions to only the most trusted and necessary administrators to reduce the risk of privilege escalation. 2. Monitor network connections between FortiGate devices to detect and block unauthorized or suspicious upstream FortiGate connections. 3. Implement strict network segmentation and access controls to limit administrative access to FortiGate management interfaces. 4. Regularly audit administrator accounts and permissions to ensure least privilege principles are enforced. 5. Deploy network intrusion detection systems (IDS) to identify anomalous traffic patterns indicative of exploitation attempts. 6. Stay updated with Fortinet advisories and apply security patches promptly once available. 7. Consider temporary compensating controls such as disabling Security Fabric features if feasible until patches are released. 8. Conduct internal penetration testing and vulnerability assessments focusing on FortiGate devices to identify potential exploitation paths.