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Re: [Full-disclosure] Microsoft Windows XP/2003/Vista memory corruption 0day

From: Michele Cicciotti (mckhamsa.net)
Date: Thu Dec 21 2006 - 18:58:19 CST


> 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

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