CVE-2019-12789

An issue was discovered on Actiontec T2200H T2200H-31.128L.08 devices, as distributed by Telus. By attaching a UART adapter to the UART pins on the system board, an attacker can use a special key sequence (Ctrl-) to obtain a shell with root privileges. After gaining root access, the attacker can mount the filesystem read-write and make permanent modifications to the device including bricking of the device, disabling vendor management of the device, preventing automatic upgrades, and permanently installing malicious code on the device.

Source: CVE-2019-12789