During last week’s Microsoft Patch Day, I pointed out that Microsoft had delayed two of the expected bulletins. This week, they released one of those delayed updates, and rate it as a Critical issue.

According to the MS14-068 Security Bulletin, Kerberos suffers from a local privilege elevation flaw that could allow attackers to gain full control of your entire domain. Kerberos is one of the authentication protocols used by Windows Servers. Kerberos Key Distribution Center (KDC) is the network service that supplies kerberos “tickets.” Unfortunately, Windows Servers suffers from a KDC vulnerability that allows local users to gain full domain administrator privileges simply by sending maliciously forged tickets to your KDC server. The good news is, an attacker needs valid domain login credentials, and local network access to leverage this flaw. The bad news is, if they can exploit the flaw, they basically gain access to ALL your Windows machines easily. This is a great flaw for advanced attackers. If they can pwn even one of your least privileged users, they can leverage it to gain full control of Windows networks, and easily move laterally throughout your network. I consider this a pretty serious issue.

I recommend you patch your Windows Servers, especially your Active Directory controller, as soon as possible. Check out the Affected Software section of Microsoft’s bulletin for patch details. Though I recommend you update quickly, your Authentication server is a critical network component. I highly recommend you test this update on a non-production server first, to make sure it doesn’t cause and unexpected problems. — Corey Nachreiner, CISSP (@SecAdept)

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The original article/video can be found at Grab Microsoft’s Out-of-Cycle Kerberos Patch