Comment It's a bit worse than what's posted here (Score 1) 20
Someone can craft a URL to send via email to a target or put into an img tag or clickable link on a website. There are plenty of ways to exploit this that don't involve communicating with servers that are directly facing the Internet. Targets can be running on localhost. The 1,800 servers mentioned are just the Internet facing servers running Windows - probably mostly people who punched holes in their network to run a server from home. But there are plenty of devs who still run Apache + PHP in the background on their local Windows machines and most large corporations run Windows, so there's a lovely exploitable vector there. And how often do devs update the software on their computer they use to develop software? They almost never do because something always breaks when updating and they don't need that. It only takes one targeted dev to wreck a whole network of machines. For example, there was that wacky SSH backdoor discovered a few months ago that would have backdoored the whole planet due to careful targeting of one specific developer.
The character set limitation is the only saving grace here. You have to be running with a Chinese or Japanese locale to be vulnerable.