Hmm... Windows has part of a HTTP stack in the kernel, which I know solely based on hearing about the recent vulnerability in it. And OS X's kernel, IIRC, can

Hmm... Windows has part of a HTTP stack in the kernel, which I know solely based on hearing about the recent vulnerability in it. And OS X's kernel, IIRC, can load disk images over HTTP for netboot purposes. That leaves Linux as the odd one out :) (Yes, I know that's completely tangential to the point you're making.)