It won't hit the Earth or the Moon, but it is passing through or near a gravitational 'keyhole'.

The keyhole is caused by the Earth's and the Moon's gravity acting on YU55 to alter its orbit. It is very possible that during this pass, its orbit will get altered enough so that on its next pass it impacts Earth!

The fact is that NASA/JPL know that its going to be very close. So close in fact that it will be years before NASA/JPL will be able to compute the new orbit with enough accuract to know if Earth gets hit on the next pass or not.

But one this in sure, NASA/JPL will never tell the public if they determine an impact event will happen.