ASUS RT-AC68U, RT-AC66R, RT-AC66U, RT-AC56R, RT-AC56U, RT-N66R, RT-N66U, RT-N56R, RT-N56U, and possibly other RT-series routers before firmware 3.0.0.4.376.x do not verify the integrity of firmware (1) update information or (2) downloaded updates, which allows man-in-the-middle (MITM) attackers to execute arbitrary code via a crafted image.