The definition of treason is extremely narrow. You might be able to make the case that he’s acting on behalf of Russia and other enemies, but it’s a stretch.

Treason against the United States, shall consist only in levying War against them, or in adhering to their Enemies, giving them Aid and Comfort.

Source: The US Constitution

No, it’s a vulnerability with PXE booting, AKA “boot to network”. While most hardware has the capability (often used to load the device in the first place), I would question how many are set to use this on a routine basis.

This sounds like something scary in a lab, but nearly useless in the real world.