CVE-2025-11848 identifies a null pointer dereference vulnerability classified under CWE-476 in the Wake-on-LAN CGI program of Zyxel VMG3625-T50B and WX3100-T0 firmware versions up to 5.50(ABPM.9.6)C0 and 5.50(ABVL.4.8)C0 respectively. This flaw arises when the software improperly handles pointers, leading to a dereference of a null pointer upon processing a specially crafted HTTP request. The vulnerability requires the attacker to be authenticated with administrator privileges, which limits exploitation to insiders or compromised admin accounts. Successful exploitation results in a denial-of-service condition, causing the device to crash or become unresponsive, thereby disrupting network availability. The CVSS v3.1 base score is 4.9, reflecting medium severity due to the absence of impact on confidentiality or integrity and the requirement for high privileges. No public exploit code or active exploitation has been reported. The vulnerability affects specific Zyxel firmware versions, and no official patches have been linked yet, indicating that mitigation currently relies on access control and monitoring. The Wake-on-LAN CGI interface is a network-exposed service, making this vulnerability relevant for network administrators managing Zyxel devices in enterprise or ISP environments.

The primary impact of CVE-2025-11848 is denial of service, which can disrupt network availability by crashing or freezing affected Zyxel devices. For organizations relying on these devices as gateways or network infrastructure components, this can lead to temporary loss of connectivity, impacting business operations, remote access, and service continuity. Since exploitation requires administrator privileges, the risk of external attackers exploiting this vulnerability is lower unless admin credentials are compromised. However, insider threats or attackers who have gained elevated access could leverage this vulnerability to cause operational disruption. The lack of impact on confidentiality or integrity means data breaches or unauthorized data modification are not direct concerns. Nevertheless, denial of service on critical network devices can indirectly affect organizational security posture by disabling monitoring or protective controls. The absence of known exploits reduces immediate risk but does not eliminate the threat, especially in environments with weak administrative controls or outdated firmware.

1. Restrict administrative access to Zyxel VMG3625-T50B and WX3100-T0 devices to trusted personnel only, using strong authentication methods such as multi-factor authentication where possible. 2. Monitor administrative accounts and network traffic for unusual activity that could indicate attempts to exploit the vulnerability. 3. Disable or restrict access to the Wake-on-LAN CGI interface if it is not required for operational purposes to reduce the attack surface. 4. Implement network segmentation to isolate management interfaces from general user networks and the internet. 5. Regularly check Zyxel’s official channels for firmware updates or patches addressing this vulnerability and apply them promptly once available. 6. Employ intrusion detection or prevention systems capable of recognizing abnormal HTTP requests targeting the Wake-on-LAN CGI program. 7. Conduct periodic security audits and vulnerability assessments on network devices to identify and remediate similar issues proactively.