A security feature bypass vulnerability exists when Windows fails to properly enforce the Windows Trusted Boot policy. An attacker who successfully exploited this vulnerability could disable code integrity checks, allowing test-signed executables and drivers to be loaded on a target device. Furthermore, an attacker could bypass Trusted Boot integrity validation for BitLocker and Device Encryption security features.
An attacker who has gained administrative privileges or who has physical access to a target device could exploit the vulnerability by applying a maliciously crafted Boot Configuration Data (BCD) setting. The security update addresses the vulnerability by improving how Windows parses BCD.

Further information on this exploit is available at : MS15-111