Why can't Microsoft or NSA or whatever good samaritan use the same vulnerability and attack vector to force-spread the update or at least a patch of some kind?
Because accessing and modifying computer systems without owner's prior agreement is a crime in most parts of the world. Why would MS, NSA or any other entity would risk potential trials?
I would be surprised if there wasn't at least a couple of paragraphs in the eula where people give much more control over to Microsoft.