Technology aside I find the scariest thing about trident to be the lack of codes in the PM's control. Everything needed to launch a nuke is already on the submarine, and it's only military discipline stopping it.
The only issues being that there is no real evidence that Wannacry diffusion is connected with machines running Windows 2000 or XP (where seemingly the malware doesn't even run) and seemingly (as stated in the El Reg article cited by detritus) the OS of the ship(s) are not connected in any way with the internet, so it would be hard for it to enter the system at all.
On the other hand..<p><a href="http://www.theregister.co.uk/2017/06/01/trident_nuclear_deterrent_submarines_hackable_lol_no/" rel="nofollow">http://www.theregister.co.uk/2017/06/01/trident_nuclear_dete...</a>