CVE-2025-13940 is a vulnerability classified under CWE-440 (Expected Behavior Violation) affecting WatchGuard Fireware OS, specifically versions from 12.8.1 through 12.11.4 and 2025.1 through 2025.1.2. The flaw allows an attacker with high-level privileges on the device to bypass the boot time system integrity check, a critical security control designed to verify the integrity of the Firebox device's firmware and software during startup. Normally, if the integrity check fails, the Firebox is expected to shut down to prevent operation under potentially compromised conditions. However, due to this vulnerability, the attacker can prevent the device from shutting down despite a failed integrity check, thereby maintaining operation of a potentially compromised system. The on-demand integrity check available through the Fireware Web UI will still report failures correctly, but this does not mitigate the risk posed by the bypass at boot time. The vulnerability requires local access with high privileges, no user interaction, and does not affect confidentiality or availability directly but impacts the integrity of the device's boot process. No known exploits have been reported in the wild, and no official patches have been linked as of the publication date. This vulnerability undermines the trust model of the Firebox security appliance, potentially allowing attackers to maintain persistence and evade detection by circumventing critical boot-time security checks.

For European organizations relying on WatchGuard Firebox devices for network security, this vulnerability poses a significant risk to the integrity and trustworthiness of their perimeter defenses. If exploited, attackers with local high-level access could maintain compromised devices in operation, potentially allowing persistent unauthorized access or the installation of malicious firmware or software components. This could lead to undetected network breaches, data exfiltration, or lateral movement within corporate networks. The inability of the device to shut down upon integrity check failure undermines the security posture and could delay incident response or forensic investigations. While the vulnerability does not directly impact confidentiality or availability, the integrity compromise can indirectly facilitate broader attacks. Organizations in critical infrastructure, finance, healthcare, and government sectors in Europe, which often deploy WatchGuard Firebox appliances, are particularly at risk. The absence of known exploits in the wild suggests limited immediate threat, but the medium severity rating and the nature of the vulnerability warrant prompt attention to prevent future exploitation.

European organizations should implement the following specific mitigations: 1) Immediately inventory and identify all WatchGuard Firebox devices running affected Fireware OS versions (12.8.1 through 12.11.4 and 2025.1 through 2025.1.2). 2) Restrict administrative access to Firebox devices to trusted personnel and secure management interfaces using strong authentication and network segmentation to minimize the risk of local high-privilege compromise. 3) Monitor system integrity check results via the Fireware Web UI regularly and investigate any reported failures promptly. 4) Employ host-based and network intrusion detection systems to detect anomalous behavior indicative of attempts to bypass boot integrity checks or maintain persistence. 5) Coordinate with WatchGuard support for any forthcoming patches or updates addressing this vulnerability and plan for timely deployment once available. 6) Consider implementing additional endpoint security controls and network segmentation to limit the impact of a compromised Firebox device. 7) Conduct regular security audits and penetration testing focused on device integrity and administrative access controls. These measures go beyond generic advice by focusing on access control hardening, active monitoring, and incident response preparedness tailored to this specific vulnerability.