Not that long ago an attack was posited. Use the fact that memory cells are adjacent, that silicon geometry is getting smaller, and that capacitive coupling could cause one cell to influence another.
Now there is another implementation, 'drammer' (AKA Flip Feng Shui). And it runs as an android app. Got a nexus 4 and want root? this is your tool. Any user can be root, any time. For simple.