CVE-2025-11846 is a null pointer dereference vulnerability categorized under CWE-476 found in the account settings 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. The vulnerability arises when an authenticated attacker with administrator privileges sends a specially crafted HTTP request to the affected CGI endpoint, causing the firmware to dereference a null pointer. This leads to a denial-of-service (DoS) condition, effectively crashing or rebooting the device and disrupting network services. The vulnerability does not allow unauthorized access or data manipulation but impacts availability. The CVSS v3.1 base score is 4.9, reflecting medium severity due to the requirement for administrative privileges and the lack of confidentiality or integrity impact. No user interaction is needed, and the attack vector is network-based, making exploitation feasible within the administrative network scope. No public exploits or patches have been published at this time, but the vulnerability has been officially assigned and disclosed by Zyxel. The flaw highlights the importance of robust input validation and error handling in embedded device firmware, especially in management interfaces exposed to network administrators.

The primary impact of CVE-2025-11846 is a denial-of-service condition on affected Zyxel devices, which can disrupt network connectivity and availability for organizations relying on these routers or gateways. This can affect enterprise networks, ISPs, and critical infrastructure sectors that use Zyxel VMG3625-T50B or WX3100-T0 devices for internet access or internal network routing. The DoS could lead to downtime, loss of productivity, and potential cascading failures in dependent systems. Since exploitation requires administrator-level access, the threat is mainly from insider attackers or attackers who have already compromised administrative credentials. The lack of confidentiality or integrity impact limits the risk of data breaches or unauthorized data modification. However, the disruption of network services can have significant operational consequences, especially in environments where continuous connectivity is critical. The absence of known exploits in the wild reduces immediate risk but does not eliminate the potential for future exploitation once the vulnerability becomes widely known.

To mitigate CVE-2025-11846, organizations should implement the following specific measures: 1) Restrict administrative access to Zyxel devices to trusted personnel and secure management networks using strong authentication and network segmentation. 2) Monitor administrative access logs for unusual activity that could indicate attempts to exploit the vulnerability. 3) Apply firmware updates from Zyxel as soon as they become available to address this vulnerability. 4) If immediate patching is not possible, consider temporarily disabling or restricting access to the vulnerable CGI account settings interface to prevent exploitation. 5) Employ network-level protections such as firewalls or intrusion prevention systems to limit access to device management interfaces from untrusted networks. 6) Conduct regular security audits and vulnerability assessments on network devices to identify and remediate similar issues proactively. 7) Educate administrators on the risks of privilege misuse and the importance of safeguarding credentials to prevent insider threats.