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Vulnerability of Windows: denials of service of win32k.sys

Synthesis of the vulnerability 

A local attacker can use the PostMessage() function, in order to generate an error in win32k.sys, which stops the system.
Vulnerable software: Windows 7, Windows Server 2000, Windows Server 2003, Windows Server 2008 R0, Windows Server 2008 R2, Windows Vista, Windows XP.
Severity of this announce: 1/4.
Number of vulnerabilities in this bulletin: 2.
Creation date: 23/04/2010.
Références of this computer vulnerability: BID-39630, BID-39631, CVE-2010-1734, CVE-2010-1735, VIGILANCE-VUL-9607.

Description of the vulnerability 

The PostMessage() function is used to send a message to a window. It uses win32k.sys. Two vulnerabilities of win32k.sys can be exploited via PostMessage().

The PostMessage() function does not check the memory address given as argument, when the message type is 0x4c (SfnLOGONNOTIFY). [severity:1/4; BID-39630, CVE-2010-1735]

The PostMessage() function does not check the memory address given as argument, when the message type is 0x18d (SfnINSTRING). [severity:1/4; BID-39631, CVE-2010-1734]

A local attacker can therefore use the PostMessage() function, in order to generate an error in win32k.sys, which stops the system.

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This computer weakness announce impacts software or systems such as Windows 7, Windows Server 2000, Windows Server 2003, Windows Server 2008 R0, Windows Server 2008 R2, Windows Vista, Windows XP.

Our Vigilance Computer Vulnerability Alerts team determined that the severity of this security alert is low.

The trust level is of type confirmed by the editor, with an origin of user shell.

This bulletin is about 2 vulnerabilities.

A proof of concept or an attack tool is available, so your teams have to process this alert. An attacker with a beginner ability can exploit this vulnerability.

Solutions for this threat 

Windows: patch for win32k.sys.
A patch is available:
Windows XP SP3
  http://www.microsoft.com/downloads/details.aspx?familyid=DEEAC521-D3A2-4019-8176-C9228E733CF4
Windows XP x64 SP2
  http://www.microsoft.com/downloads/details.aspx?familyid=D6C5455E-BC31-4842-AEF4-EBFF92324323
Windows 2003 SP2
  http://www.microsoft.com/downloads/details.aspx?familyid=59395F00-90F4-4B68-8DD3-03FF611C1BC8
Windows 2003 x64 SP2
  http://www.microsoft.com/downloads/details.aspx?familyid=9EF1C600-BB93-4800-81B8-8C64B369C194
Windows 2003 Itanium SP2
  http://www.microsoft.com/downloads/details.aspx?familyid=F96B8154-9976-41B0-B9D7-D79887FE9364
Windows Vista SP1, SP2
  http://www.microsoft.com/downloads/details.aspx?familyid=C9345207-7242-4B71-BF80-B52031E08F8C
Windows Vista x64 SP1, SP2
  http://www.microsoft.com/downloads/details.aspx?familyid=1620E7AC-3913-478D-8120-E9F46D98F453
Windows Server 2008 32-bit Gold, SP2
  http://www.microsoft.com/downloads/details.aspx?familyid=A8B1A3F7-7147-494E-BFC0-B1979B9578E6
Windows Server 2008 x64 Gold, SP2
  http://www.microsoft.com/downloads/details.aspx?familyid=C1C25CB7-7E82-4C14-9666-AFF52DD308B4
Windows Server 2008 Itanium Gold, SP2
  http://www.microsoft.com/downloads/details.aspx?familyid=45FE5135-AA89-4F60-8CDB-EC0EDC9A7E77
Windows 7 for 32-bit
  http://www.microsoft.com/downloads/details.aspx?familyid=68BDDF4B-B597-477E-80E4-9293D7160496
Windows 7 for x64
  http://www.microsoft.com/downloads/details.aspx?familyid=5FF09E03-D662-4B23-AB26-D25CA2BA58DF
Windows Server 2008 R2 for x64
  http://www.microsoft.com/downloads/details.aspx?familyid=6BBC9CB1-0B59-4473-ADF9-2CE2F0F94C0A
Windows Server 2008 R2 for Itanium
  http://www.microsoft.com/downloads/details.aspx?familyid=2543191A-09CB-4417-BBB2-AAC4D9A2A756
The Microsoft announce indicates workarounds.

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