> Holy mackerel! Instances of this bug date back to 1999!
Different bug. That appears to be a trivial exhaustion of CSRSS worker threads through indiscriminate calls to MessageBox+MB_SERVICE_NOTIFICATION, which causes a DoS as no threads are available to serve kernel-mode requests from win32k, stalling GUI processes. I have done my fair share of CSRSS reversing in my better days, and I'm pretty sure that in Windows 2000 and later, a dedicated thread is used for such notifications, not just any thread, any time. Easily verifiable with local net sends and Spy++. It wasn't a "bug" either, more like a serious design flaw that ignored a very basic Win32 mantra ("don't do GUI in a worker thread") - not at all like this double-free
