The CryptProtectMemory function in cng.sys (aka the Cryptography Next Generation driver) in the kernel-mode drivers in Microsoft Windows Server 2003 SP2, Windows Vista SP2, Windows Server 2008 SP2 and R2 SP1, Windows 7 SP1, Windows 8, Windows 8.1, Windows Server 2012 Gold and R2, and Windows RT Gold and 8.1, when the CRYPTPROTECTMEMORY_SAME_LOGON option is used, does not check an impersonation token's level, which allows local users to bypass intended decryption restrictions by leveraging a service that (1) has a named-pipe planting vulnerability or (2) uses world-readable shared memory for encrypted data, aka "CNG Security Feature Bypass Vulnerability" or MSRC ID 20707.
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2015/ms15-010