CVE-2024-51248 is a command injection vulnerability identified in the Draytek Vigor3900 router firmware version 1.5.1.3. The vulnerability resides in the web management interface, specifically within the mainfunction.cgi script's modifyrow function. Attackers with low privileges (PR:L) can remotely inject arbitrary OS commands without requiring user interaction (UI:N) by manipulating parameters sent to this CGI endpoint. The vulnerability is remotely exploitable over the network (AV:A), meaning the attacker must have access to the local network or VPN to reach the management interface. Successful exploitation allows full compromise of the device, impacting confidentiality, integrity, and availability (C:H/I:H/A:H). This is classified under CWE-78 (Improper Neutralization of Special Elements used in an OS Command). No patches or public exploits are currently available, but the high CVSS score (8.0) reflects the severity and potential impact. The flaw enables attackers to execute arbitrary commands, potentially leading to device takeover, network disruption, or pivoting to internal networks.

The vulnerability poses a severe risk to organizations using Draytek Vigor3900 routers, as it allows attackers to execute arbitrary commands with low privileges remotely. This can lead to full device compromise, exposing sensitive network configurations and data. Attackers could disrupt network availability by altering routing or firewall rules, intercept or manipulate traffic, and use the compromised device as a foothold for further attacks within the internal network. Given the critical role of routers in network infrastructure, exploitation could cause significant operational downtime, data breaches, and loss of trust. The lack of public exploits currently reduces immediate risk, but the vulnerability’s characteristics make it a prime target for attackers once exploit code becomes available.

1. Immediately restrict access to the router’s management interface to trusted IP addresses only, ideally via VPN with strong authentication. 2. Disable remote management if not required or move it to a secure management VLAN isolated from general user networks. 3. Monitor network traffic and device logs for unusual commands or access patterns targeting mainfunction.cgi or modifyrow function. 4. Apply any available firmware updates from Draytek as soon as they are released addressing this vulnerability. 5. If patches are not yet available, consider temporary compensating controls such as web application firewalls (WAF) or intrusion prevention systems (IPS) to detect and block command injection attempts. 6. Conduct regular security audits of network devices and enforce least privilege principles for administrative access. 7. Educate network administrators about this vulnerability and ensure incident response plans include steps for compromised network devices.