Null pointer dereference

The IsHandleEntrySecure function in win32k.sys in the kernel-mode drivers in Microsoft Windows Server 2008 SP2 does not properly validate the tagPROCESSINFO pW32Job field, which allows local users to cause a denial of service (NULL pointer dereference and system crash) via a crafted NtUserValidateHandleSecure call for an owned object. NOTE: the vendor reportedly disputes the significance of this report, stating that "it appears to be a local DOS … we don’t consider it a security vulnerability.