CVE-2024-51249 is a command injection vulnerability identified in the Draytek Vigor3900 router firmware version 1.5.1.3. The flaw resides in the handling of requests to the mainfunction.cgi endpoint, particularly the reboot function, where insufficient input validation allows an attacker to inject arbitrary commands. This vulnerability is classified under CWE-78 (Improper Neutralization of Special Elements used in an OS Command), indicating that user-supplied input is not properly sanitized before being passed to system-level command execution. The attacker requires low privileges (PR:L) and no user interaction (UI:N) to exploit this vulnerability remotely (AV:A), meaning the attacker must have some network access to the device but does not need to trick a user. The vulnerability impacts confidentiality, integrity, and availability (C:H/I:H/A:H), as arbitrary command execution can lead to data theft, device manipulation, or denial of service. The CVSS 3.1 vector score of 8.0 reflects these factors. No patches or exploits are currently publicly available, but the vulnerability is published and should be considered critical for affected users. Given the device’s role as a network gateway, exploitation could have severe consequences for organizational network security.

The potential impact of CVE-2024-51249 is significant for organizations relying on Draytek Vigor3900 routers. Successful exploitation allows attackers to execute arbitrary commands on the device, potentially leading to full device compromise. This can result in unauthorized access to internal networks, interception or manipulation of network traffic, disruption of network services through forced reboots or configuration changes, and pivoting to other internal systems. The confidentiality of sensitive data traversing the network can be compromised, integrity of network configurations can be undermined, and availability of network services can be disrupted. Organizations in sectors such as telecommunications, finance, government, and critical infrastructure that use these routers as part of their network perimeter are particularly at risk. The vulnerability’s ease of exploitation with low privileges and no user interaction increases the likelihood of targeted attacks or automated exploitation once public exploits emerge.

To mitigate CVE-2024-51249, organizations should take immediate steps beyond waiting for an official patch: 1) Restrict access to the router’s management interfaces (especially mainfunction.cgi) by implementing strict firewall rules and limiting access to trusted IP addresses only. 2) Employ network segmentation to isolate the router management network from general user and internet-facing networks. 3) Monitor network traffic and device logs for unusual commands or reboot requests that could indicate exploitation attempts. 4) Disable or restrict the reboot function remotely if possible, or require stronger authentication mechanisms for management functions. 5) Use intrusion detection/prevention systems (IDS/IPS) to detect command injection patterns targeting the CGI endpoint. 6) Regularly back up router configurations to enable rapid recovery in case of compromise. 7) Stay informed on vendor advisories and apply firmware updates promptly once patches are released. 8) Consider deploying compensating controls such as VPN access for management interfaces to reduce exposure.