Public Vulnerability Reports

NGSEC StackDefender 2.0 Invalid Pointer Dereference Vulnerability



StackDefender is an IPS (Intrusion Prevention System), for Win32
platforms, that will deny shellcode from executing in User Stack and
Writable memory regions. StackDefender uses PAX technology for this


StackDefender offers protection by hooking ZwAllocateVirtualMemory and
ZwProtectVirtualMemory functions. These two kernel API's are responsible
for allocating and protecting memory. The ZwProtectVirtualMemory
function declaration is as follows:

   ZwProtectVirtualMemory(HANDLE ProcessHandle, PVOID *BaseAddress,
      PULONG ProtectSize, ULONG NewProtect, PULONG OldProtect);

The problem specifically exists because StackDefender fails to verify
'BaseAddress' as a valid address prior dereferencing it as a pointer.


Successful exploitation allows remote attackers to cause the underlying
system to crash. This is possible by specifying an invalid address for
'BaseAddress'. Exploitation requires that an attacker has an
exploitation vector to the system that StackDefender attempts to block.


iDEFENSE has confirmed the existence of this vulnerability in the latest
version of StackDefender, version 2.0.


iDEFENSE is currently unaware of any workarounds for this issue.


The vendor has released the following patch fixing this issue:


The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CAN-2004-0766 to this issue. This is a candidate for inclusion in
the CVE list (, which standardizes names for
security problems.


07/10/2004    Vulnerability discovered by iDEFENSE
07/12/2004    Initial vendor notification
07/22/2004    Initial vendor response
08/03/2004    Public disclosure


Peter Silberman (iDEFENSE Labs) is credited with the discovery of this

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Copyright © 2004 Verisign, Inc.

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