The kernel in Microsoft Windows 8, Windows 8.1, Windows Server 2012 Gold and R2, and Windows RT Gold and 8.1 does not properly validate an unspecified address, which allows local users to bypass the KASLR protection mechanism, and consequently discover the cng.sys base address, via a crafted application, aka "Windows Kernel Security Feature Bypass Vulnerability."
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2015/ms15-052