Few days ago, Microsoft released a security update, classified as Important (for Windows Server products), that addresses a vulnerability in Active Directory. The affected Windows version are listed in the Security Bulletin page and you should know that Windows Server 2012 is affected as well.
The vulnerability could allow denial of service if an attacker sends a specially crafted query to the Lightweight Directory Access Protocol (LDAP) service. The security update addresses the vulnerability by correcting how the LDAP service handles specially crafted LDAP queries
The update will be delivered automatically through the Windows Update service but you can also download the update manually from the Security Bulletin page.
More information: Vulnerability in Active Directory Could Lead to Denial of Service (2830914)
Good Luck!
