An arbitrary code execution vulnerability exisits in Linksys WRT54GL Wireless-G Broadband Router with firmware <= 4.30.18.006. The Check_TSSI function within the httpd binary uses unvalidated user input in the construction of a system command. An authenticated attacker with administrator privileges can leverage this vulnerability over the network via a malicious POST request to /apply.cgi to execute arbitrary commands on the underlying Linux operating system as root.