One can gain root access on the Foxconn femtocell FEMTO AP-FC4064-T version AP_GT_B38_5.8.3lb15-W47 LTE Build 15 via UART pins without any restrictions, which leads to full system compromise and disclosure of user communications.
https://gist.github.com/DrmnSamoLiu/cd1d6fa59501f161616686296aa4a6c8