CVE-2025-59396 identifies a critical security vulnerability in WatchGuard Firebox network security appliances. The issue arises from the default device configuration that enables SSH administrative access on a non-standard port (4118) using a default 'readwrite' password for the admin account. This default credential is widely known and documented, allowing attackers to remotely connect via SSH and gain full administrative privileges without needing to authenticate further or trick users into interaction. The vulnerability affects all devices configured up to September 10, 2025, with no specific version restrictions provided. The lack of a CVSS score indicates this is a newly published vulnerability with limited public data, but the technical details suggest a severe risk due to the direct administrative access granted. No patches or official remediation guidance have been published as of now, and no active exploitation has been reported. The vulnerability's exploitation could lead to complete compromise of the Firebox device, enabling attackers to manipulate firewall rules, intercept or redirect traffic, disable security features, or launch further attacks within the network. The use of a non-standard SSH port (4118) may reduce casual detection but does not mitigate the risk. Given the critical role of Firebox devices in perimeter defense and network segmentation, this vulnerability poses a significant threat to organizations relying on these appliances for network security.

For European organizations, the impact of CVE-2025-59396 could be substantial. WatchGuard Firebox devices are commonly deployed in enterprise, government, and critical infrastructure environments across Europe to provide firewall, VPN, and intrusion prevention services. Unauthorized administrative access could lead to full device compromise, allowing attackers to disable security controls, exfiltrate sensitive data, or pivot to internal networks. This could result in data breaches, service disruptions, and loss of confidentiality, integrity, and availability of network resources. The vulnerability's exploitation could also undermine trust in network security architectures and lead to regulatory non-compliance under GDPR and other data protection laws. Organizations in sectors such as finance, healthcare, energy, and public administration are particularly at risk due to their reliance on robust perimeter defenses and the sensitivity of their data. The absence of known exploits currently provides a window for proactive mitigation, but the ease of exploitation and default credential usage make rapid response essential to prevent potential attacks.

Organizations should immediately audit all WatchGuard Firebox devices to identify those configured before September 10, 2025. The highest priority mitigation is to change the default 'readwrite' password for the admin account to a strong, unique password. Additionally, administrators should disable SSH access on port 4118 if not required or restrict it to trusted management IP addresses using firewall rules or access control lists. Network monitoring should be enhanced to detect unauthorized SSH connections on port 4118. Where possible, multi-factor authentication (MFA) should be enabled for administrative access to add an additional security layer. Organizations should also review device firmware and configuration management policies to ensure secure baseline configurations and timely updates once patches become available. Incident response plans should be updated to include detection and remediation steps for this vulnerability. Finally, organizations should engage with WatchGuard support and subscribe to security advisories to receive updates on patches or further guidance.