Are ungrounded three-way switches dangerous?
This looks to be wired correctly prior to the current code 2014 with the exception the white wire in the second box should be marked with tape black or red just not green or white. If there are metal boxes and the boxes are grounded things would be fine but you probably have plastic boxes so adding the ground to the switch would be a good idea. You did not mention if there is a ground in the second box there should be. And it should be connected to the switch also. The main difference in your wiring and current code is that the neutral needs to be run to the 2nd box with the ground and other 3. With the grounds added to the switch(s) it would be safe, with the whit leg identified as a Curren carying conductor, this would be up to code prior to 2014. your state may be on an older version of code so depending on that it could still be up to date with the changes.