An elevation of privilege vulnerability in the bootloader could enable a local attacker to execute arbitrary modem commands on the device. This issue is rated as High because it is a local permanent denial of service (device interoperability: completely permanent or requiring re-flashing the entire operating system). Product: Android. Versions: N/A. Android ID: A-30308784.
https://source.android.com/security/bulletin/2017-01-01.html
https://securityintelligence.com/android-vulnerabilities-attacking-nexus-6-and-6p-custom-boot-modes/