The Client/Server Run-time Subsystem (aka CSRSS) in the Win32 subsystem in Microsoft Windows XP SP2 and SP3, Windows Server 2003 SP2, Windows Vista SP1 and SP2, and Windows Server 2008 Gold and SP2 does not ensure that an unspecified array index has a non-negative value before performing read and write operations, which allows local users to gain privileges or cause a denial of service (memory corruption) via a crafted application that triggers an incorrect memory assignment for a user transaction, aka "CSRSS Local EOP SrvSetConsoleNumberOfCommand Vulnerability."
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A12362
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2011/ms11-056