Why is Microsoft updating Windows PCs for a security bug on the server?

The Kerberos vulnerability is only in Windows Server, but Windows PCs are getting extra security fixes

When Microsoft released a critical update for multiple versions of Windows Server this month, it also pushed out a fix for several releases of the Windows client OS, including even the technical preview for Windows 10.

It was critical to get the patch out for Windows Server: An exploit affecting Windows Server 2008 R2 and earlier versions has already been detected, and Windows Server 2012 and later releases are vulnerable to a related but more difficult attack.

But the vulnerability isn't present in the desktop versions of Windows. In Windows Server, the flaw allows attackers to employ the username and password of anyone in an Active Directory domain to get the same system privileges as a domain administrator, using a forged Privilege Attribute Certificate to fool the Kerberos Domain Controller that manages remote access.

The bulletin for the patch says there's no security impact for the client versions of Windows. So why did Microsoft also release an update for Windows Vista, Windows 7, Windows 8, Windows 8.1 and the Windows 10 Technical Preview?

It's because although they don't have that specific vulnerability, looking into the Windows source code to understand how the Privilege Attribute Certificate could be forged revealed some older code that Microsoft was no longer satisfied with, a representative for the company told us. That could mean other potential attacks, although they declined to give more details.

"The 'hardening' on the client side is the replacement of older code with newer code. In our investigation, although we did not discover a vulnerability on these platforms, we did discover code that needed to be improved in order to meet our current security standards," the representative said.

Although Microsoft hasn't said whether Windows XP also had the problem code, it's likely it does given the age of the code involved. As XP is out of support, only companies that are paying for extended support contracts would get an update for it -- another incentive for anyone still using the older OS to upgrade.

The update applied to the Windows Server Technical Preview as well, but Microsoft said it doesn't list security impact and severity ratings for previews. "As customers know, beta software is not fully supported and we do not want to cause customer confusion," the representative said.

Join the newsletter!

Or

Sign up to gain exclusive access to email subscriptions, event invitations, competitions, giveaways, and much more.

Membership is free, and your security and privacy remain protected. View our privacy policy before signing up.

Error: Please check your email address.

Tags Microsoftoperating systemssoftwareWindowspatches

Keep up with the latest tech news, reviews and previews by subscribing to the Good Gear Guide newsletter.
Mary Branscombe

Mary Branscombe

IDG News Service
Show Comments

Cool Tech

Toys for Boys

Family Friendly

Stocking Stuffer

SmartLens - Clip on Phone Camera Lens Set of 3

Learn more >

Christmas Gift Guide

Click for more ›

Brand Post

Most Popular Reviews

Latest Articles

Resources

PCW Evaluation Team

Aysha Strobbe

Microsoft Office 365/HP Spectre x360

Microsoft Office continues to make a student’s life that little bit easier by offering reliable, easy to use, time-saving functionality, while continuing to develop new features that further enhance what is already a formidable collection of applications

Michael Hargreaves

Microsoft Office 365/Dell XPS 15 2-in-1

I’d recommend a Dell XPS 15 2-in-1 and the new Windows 10 to anyone who needs to get serious work done (before you kick back on your couch with your favourite Netflix show.)

Maryellen Rose George

Brother PT-P750W

It’s useful for office tasks as well as pragmatic labelling of equipment and storage – just don’t get too excited and label everything in sight!

Cathy Giles

Brother MFC-L8900CDW

The Brother MFC-L8900CDW is an absolute stand out. I struggle to fault it.

Luke Hill

MSI GT75 TITAN

I need power and lots of it. As a Front End Web developer anything less just won’t cut it which is why the MSI GT75 is an outstanding laptop for me. It’s a sleek and futuristic looking, high quality, beast that has a touch of sci-fi flare about it.

Emily Tyson

MSI GE63 Raider

If you’re looking to invest in your next work horse laptop for work or home use, you can’t go wrong with the MSI GE63.

Featured Content

Product Launch Showcase

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?