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[Full-disclosure] MS05-021 Microsoft Exchange X-LINK2STATE Heap Overflow PoC

From: Evgeny Pinchuk (EvgenyPRadware.com)
Date: Tue Apr 19 2005 - 12:46:49 CDT

Vulnerability Details
=====================
The vulnerability is a heap overflow in SvrAppendReceivedChunk function
which is located in xlsasink.dll.
When transmitting large chunks with X-LINK2STATE verb it is possible to
overflow the heap and perform arbitrary memory write in RtlAllocateHeap
function.
77fcc663 8901 mov [ecx],eax
77fcc665 894804 mov [eax+0x4],ecx
We are controlling ECX and EAX registers. So rewriting
lpTopLevelExceptionFilter can easily get us to our shellcode on the
heap.

Regards,

Evgeny Pinchuk

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