Severity Rating: Important
Revision Note: V1.2 (April 7, 2016): Updated the footnotes following the Affected Software and Vulnerability Severity Ratings table to further clarify installation order for security update 3101746 in MS15-115, 3081320 in MS15-121, and 3101246 in MS15-122. This is an informational change only. Customers who have already successfully installed the update do not need to take any action.
Summary: This security update resolves a security feature bypass in Microsoft Windows. An attacker could bypass Kerberos authentication on a target machine and decrypt drives protected by BitLocker. The bypass can be exploited only if the target system has BitLocker enabled without a PIN or USB key.