CVE-2025-9242 is a critical out-of-bounds write vulnerability (CWE-787) found in WatchGuard Fireware OS, specifically impacting versions 11.10.2 through 11.12.4_Update1, 12.0 through 12.11.3, and 2025.1. The vulnerability exists in the handling of VPN connections using IKEv2 protocol, affecting both Mobile User VPN and Branch Office VPN configurations when set up with a dynamic gateway peer. An out-of-bounds write occurs when the software writes data outside the boundaries of allocated memory, which can corrupt memory and potentially allow an attacker to execute arbitrary code remotely. This vulnerability is exploitable without any authentication or user interaction, making it particularly dangerous. The CVSS 4.0 base score of 9.3 reflects its critical severity, with attack vector network (AV:N), low attack complexity (AC:L), no privileges required (PR:N), no user interaction (UI:N), and high impact on confidentiality, integrity, and availability (VC:H/VI:H/VA:H). Exploitation could lead to full system compromise of the affected Fireware OS devices, which are commonly used as network security appliances such as firewalls and VPN gateways. No known exploits are currently reported in the wild, but the vulnerability's characteristics suggest that weaponization is likely to occur rapidly once details become widely available. The lack of available patches at the time of publication further increases the urgency for mitigation and risk management.

For European organizations, the impact of this vulnerability is significant due to the widespread use of WatchGuard Fireware OS in enterprise network security infrastructure, including VPN gateways that facilitate remote access and branch office connectivity. Successful exploitation could allow attackers to bypass network defenses, gain unauthorized access to internal networks, exfiltrate sensitive data, disrupt business operations, or deploy ransomware and other malware. Given the critical nature of the vulnerability and its remote, unauthenticated exploitability, it poses a direct threat to confidentiality, integrity, and availability of corporate networks. Organizations relying on WatchGuard devices for secure remote access, especially those with distributed workforces or multiple branch offices, are at heightened risk. The vulnerability could also undermine trust in secure communications and potentially expose regulated data, leading to compliance violations under GDPR and other European data protection laws. The absence of known exploits currently provides a narrow window for proactive defense, but the critical severity score and ease of exploitation necessitate immediate attention.

1. Immediate mitigation should focus on isolating affected WatchGuard Fireware OS devices from untrusted networks where possible, especially restricting VPN access until patches or workarounds are applied. 2. Monitor network traffic for unusual VPN connection attempts or anomalies that could indicate exploitation attempts. 3. Implement strict network segmentation to limit lateral movement in case of compromise. 4. Engage with WatchGuard support to obtain any available patches, hotfixes, or recommended configuration changes as soon as they are released. 5. Temporarily disable or restrict the use of dynamic gateway peer configurations in IKEv2 VPN setups if feasible, as this configuration is directly implicated in the vulnerability. 6. Employ intrusion detection/prevention systems (IDS/IPS) with updated signatures to detect exploitation attempts once available. 7. Conduct thorough audits of VPN logs and device configurations to identify any signs of compromise. 8. Prepare incident response plans specifically addressing potential exploitation of this vulnerability, including containment and recovery procedures. 9. Educate network administrators about the vulnerability and ensure they follow secure configuration best practices for VPN services.