Windows Updates Fix Relatively Minor Kernel and Kerberos Flaws

Severity: Medium


  • These vulnerabilities affect: All current versions of Windows and the components that ship with it
  • How an attacker exploits them: Multiple vectors of attack, including sending specially crafted network traffic and enticing users to run malicious applications
  • Impact: In the worst case, a local attacker can gain complete control of your Windows computer
  • What to do: Install the appropriate Microsoft patches as soon as possible, or let Windows Automatic Update do it for you.


Today, Microsoft released two security bulletins describing vulnerabilities that affect Windows and components that ship with it. Each vulnerability affects different versions of Windows to varying degrees. We summarize these Windows bulletins below:

  • MS12-068: Kernel Elevation of Privilege Vulnerability

The kernel is the core component of any computer operating system. The Windows kernel suffers from an integer overflow vulnerability, which attackers can leverage to  elevate their privilege. By running a specially crafted program, a local attacker could exploit this flaw to gain complete control of your PC. However, the attacker would first need to gain local access to your Windows computer using valid credentials. This factor significantly reduces the severity of the issue

Microsoft rating: Important

Kerberos is one of the authentication protocols used by Windows Servers. The Kerberos service suffers from a Denial of Service (DoS) vulnerability involving the way it handles specially crafted session requests. By sending specially crafted network traffic, an attacker could leverage this flaw to crash and restart your Kerberos server. The attacker could repeatedly exploit this vulnerability to keep your server offline for as long as they continued their attack. That said, most administrators do not allow Internet-based users access to their Kerberos server, which significantly mitigates the severity of this vulnerability

Microsoft rating: Important

Solution Path:

Microsoft has released Windows patches that correct all of these vulnerabilities. You should download, test, and deploy the appropriate Windows patches throughout your network immediately. If you choose, you can also let Windows Update automatically download and install these updates for you.

The links below point directly to the “Affected and Non-Affected Software” section of each bulletin, where you can find the various updates:

For All WatchGuard Users:

Though WatchGuard’s XTM appliances can mitigate some of these attacks, by preventing Internet-based attackers from accessing the vulnerable services, it cannot prevent local attacks. Therefore, we recommend you install Microsoft’s updates  to completely protect yourself from these flaws.


Microsoft has released patches correcting these issues.


This alert was researched and written by Corey Nachreiner, CISSP (@SecAdept).

What did you think of this alert? Let us know at

About Corey Nachreiner

Corey Nachreiner has been with WatchGuard since 1999 and has since written more than a thousand concise security alerts and easily-understood educational articles for WatchGuard users. His security training videos have generated hundreds of letters of praise from thankful customers and accumulated more than 100,000 views on YouTube and Google Video. A Certified Information Systems Security Professional (CISSP), Corey speaks internationally and is often quoted by other online sources, including C|NET, eWeek, and Slashdot. Corey enjoys "modding" any technical gizmo he can get his hands on, and considers himself a hacker in the old sense of the word.


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