Amlogic pppoe_wrapper Command Injection via AF_UNIX Socket

The pppoe_wrapper vendor daemon from the Amlogic Android SDK, as shipped on Nexbox A95X (Amlogic S905/S905X) TV boxes, contains a command injection vulnerability that allows local attackers to execute arbitrary commands as root by sending crafted messages to a world-writable AF_UNIX datagram socket at /dev/socket/pppoe_wrapper. Attackers can send a message beginning with 'pppd pty' followed by shell metacharacters and arbitrary commands, which are passed unfiltered to system(3) and executed by /system/bin/sh -c as root, resulting in full privilege escalation.