Microsoft downplays threat of new Windows zero-day

Hasn't found a way to hijack PCs using SMB bug

Microsoft yesterday downplayed the threat posed to Windows users by a recently-revealed vulnerability, saying that it was unlikely the bug could be exploited to compromise a computer.

The flaw in the Windows Server Message Block (SMB) network and file-sharing protocol was disclosed Monday by someone identified only as " Cupidon-3005" on the Full Disclosure security mailing list. Cupidon-3005 posted proof-of-concept code to the list.

French and Danish researchers later said hackers might be able to exploit the bug to hijack Windows PCs.

On Wednesday, Microsoft said that wasn't so.

"Based on our initial investigation this vulnerability cannot be leveraged for remote code execution (RCE) on 32-bit platforms," said Jerry Bryant, a general manager in the Microsoft Security Response Center (MSRC). "We are still investigating the possibility of code execution on 64-bit platforms, but so far have not found a likely scenario that would result in reliable code execution."

A successful attack that exploits the SMB bug would instead result in a "denial of service," said Bryant, using the term that describes a Window crash that would require rebooting the PC. Windows crashes often inform users of the dire situation with the infamous "Blue Screen of Death."

In a explanatory blog post , MSRC engineer Mark Wodrich echoed Bryant's take on the likelihood of remote code execution, saying that it was impossible on a 32-bit version of Windows due to memory limitations, and feasible on 64-bit Windows only if more than 8GB of memory was present.

Even then, said Wodrich, "We feel that triggering any such timing condition reliably will be very difficult."

HD Moore, chief security at Rapid7 and the creator of the open-source Metasploit penetration toolkit, chimed in as well.

"We haven't seen any solid examples of code execution yet, even if it turns out to be possible," Moore said in an e-mail reply to questions Wednesday. He added that a Metasploit researcher was also examining the bug and Cupidon-3005's published attack code to see if a reliable Metasploit exploit module could be crafted.

All versions of Windows contain the bug, said Wodrich, but servers running as the Primary Domain Controller (PDC) -- the system that controls the network domain -- are most vulnerable.

Microsoft pegged the vulnerability's Exploitability Index ranking at "3," meaning the company doesn't expect reliable attack code will appear in the next 30 days.

Some researchers chastised Microsoft for downplaying the threat.

"Microsoft is now calling any hard-to-exploit vulnerability (e.g. SMB) a 'Denial of Service'! What's next?" asked French security firm Vupen in a tweet earlier today .

"They've been doing this forever, MSRC is about managing PR incidents, not improving security," said Tavis Ormandy in a reply to Vupen's tweet.

Ormandy, a Google security engineer, has butted heads with Microsoft before -- most notably last summer, when he released exploit code for a bug in Windows' Help and Support Center after he said Microsoft refused to set a patch deadline.

Microsoft's Bryant said the MSRC researchers are will investigating the bug, and would issue a patch or a workaround to protect users.

Although the company's next regularly-scheduled Patch Tuesday is three weeks away, it's unlikely a fix will be delivered then unless a large number of in-the-wild attacks exploiting the vulnerability appear.

Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer or subscribe to Gregg's RSS feed . His e-mail address is gkeizer@computerworld.com .

Read more about security in Computerworld's Security Topic Center.

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 systemssoftwareWindows

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

Gregg Keizer

Computerworld (US)
Show Comments

Brand Post

Most Popular Reviews

Latest Articles

Resources

PCW Evaluation Team

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.

Laura Johnston

MSI GS65 Stealth Thin

If you can afford the price tag, it is well worth the money. It out performs any other laptop I have tried for gaming, and the transportable design and incredible display also make it ideal for work.

Andrew Teoh

Brother MFC-L9570CDW Multifunction Printer

Touch screen visibility and operation was great and easy to navigate. Each menu and sub-menu was in an understandable order and category

Featured Content

Product Launch Showcase

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?