CVE-2025-46776 is a classic buffer overflow vulnerability identified in multiple versions of Fortinet's FortiExtender product, specifically versions 7.0.0, 7.2.0, 7.4.0 through 7.4.6, and 7.6.0 through 7.6.1. The flaw arises from a buffer copy operation that does not properly validate the size of input data when processing CLI commands. This unchecked input size allows an authenticated user with high privileges to craft malicious CLI commands that overflow the buffer, potentially leading to arbitrary code execution or command injection on the affected device. The vulnerability requires the attacker to have authenticated access with elevated privileges (PR:H), no user interaction is necessary (UI:N), and the attack vector is local (AV:L), meaning the attacker must have direct or network access to the device’s CLI interface. The vulnerability impacts confidentiality, integrity, and availability (C:H/I:H/A:H), indicating that successful exploitation could lead to full compromise of the device. The CVSS v3.1 score is 6.3, categorized as medium severity, reflecting the complexity and prerequisites for exploitation. No public exploits or active exploitation in the wild have been reported to date. FortiExtender devices are typically used to extend network connectivity, often in critical infrastructure or enterprise environments, making this vulnerability significant for organizations relying on these devices for secure network extension. The lack of available patches at the time of reporting necessitates immediate risk mitigation through access controls and monitoring.

For European organizations, the impact of CVE-2025-46776 could be substantial, especially for those deploying FortiExtender devices in critical network extension roles such as remote site connectivity, industrial control systems, or telecommunications infrastructure. Successful exploitation could allow an attacker with authenticated high-level access to execute arbitrary code, potentially leading to full device compromise. This could result in unauthorized data access, disruption of network services, or use of the compromised device as a pivot point for further attacks within the network. Given the device’s role in extending network connectivity, availability disruptions could affect business continuity and operational technology environments. Confidentiality breaches could expose sensitive data traversing these devices. The requirement for authenticated high privileges limits the attack surface but does not eliminate risk, particularly if credential compromise or insider threats exist. The absence of known exploits in the wild currently reduces immediate risk but should not lead to complacency. European organizations with Fortinet FortiExtender deployments should consider this vulnerability a significant risk to network security and operational stability.

1. Restrict administrative and CLI access to FortiExtender devices strictly to trusted personnel and secure management networks using network segmentation and access control lists (ACLs). 2. Implement strong authentication mechanisms, including multi-factor authentication (MFA), to reduce the risk of credential compromise for accounts with high privileges. 3. Monitor device logs and network traffic for unusual CLI command patterns or unauthorized access attempts that could indicate exploitation attempts. 4. Apply principle of least privilege by limiting the number of users with high-level access to the device CLI. 5. Regularly audit and rotate credentials used for device management to minimize risk from leaked or stolen credentials. 6. Stay informed on Fortinet’s security advisories and apply patches or firmware updates promptly once available to remediate the vulnerability. 7. Employ network intrusion detection/prevention systems (IDS/IPS) tuned to detect anomalous behavior related to FortiExtender management interfaces. 8. Consider deploying compensating controls such as jump servers or bastion hosts for device management to add an additional layer of security.