Use-after-free vulnerability in the kernel-mode drivers in Microsoft Windows Vista SP1 and SP2 and Server 2008 Gold and SP2 allows local users to gain privileges or cause a denial of service (system crash) by using a large number of calls to the NtUserCheckAccessForIntegrityLevel function to trigger a failure in the LockProcessByClientId function, leading to deletion of an in-use process object, aka "Win32k Reference Count Vulnerability."
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A12215
https://exchange.xforce.ibmcloud.com/vulnerabilities/60120
http://www.us-cert.gov/cas/techalerts/TA10-285A.html