Millions of websites affected by unpatched flaw in Microsoft IIS 6 web server

An exploit for a zero-day vulnerability in Microsoft IIS 6.0 was published online, increasing the risk of attacks

IDG

IDG

A proof-of-concept exploit has been published for an unpatched vulnerability in Microsoft Internet Information Services 6.0, a version of the web server that's no longer supported but still widely used.

The exploit allows attackers to execute malicious code on Windows servers running IIS 6.0 with the privileges of the user running the application. Extended support for this version of IIS ended in July 2015 along with support for its parent product, Windows Server 2003.

Even so, independent web server surveys suggest that IIS 6.0 still powers millions of public websites. In addition, many companies might still run web applications on Windows Server 2003 and IIS 6.0 inside their corporate networks, so this vulnerability could help attackers perform lateral movement if they access such networks through other means.

There's evidence that this IIS vulnerability has been known by a limited number of attackers since at least July or August of last year. However, the publishing earlier this week of an exploit for it on GitHub makes it accessible to a larger number of hackers.

"Other threat actors are now in the stages of creating malicious code based on the original proof-of-concept (PoC) code," researchers from Trend Micro said in a blog post Wednesday.

According to the exploit's authors, the vulnerability is a buffer overflow in the ScStoragePathFromUrl function of the IIS 6.0 WebDAV service. It can be exploited through a specially crafted PROPFIND request.

Web Distributed Authoring and Versioning (WebDAV) is an extension of the standard Hypertext Transfer Protocol (HTTP) that allows users to create, change and move documents on a server. The extension supports several request methods, including PROPFIND, which is used to retrieve the properties of a resource.

Since Microsoft won't patch this vulnerability, one possible mitigation is to disable the WebDAV service on IIS 6.0 installations. Security firm ACROS Security has also developed a free "micropatch" for this vulnerability -- an unofficial patch that can be applied without restarting the affected server or even IIS process.

However, the best course of action would be to migrate affected websites to a newer IIS and Windows Server version altogether, as there are probably other vulnerabilities out there that also affect this platform and won't get patched.

A March survey by web analytics firm Netcraft revealed that around 185 million websites are still hosted on over 300,000 web servers that run Windows Server 2003.

Join the PC World newsletter!

Error: Please check your email address.

Our Back to Business guide highlights the best products for you to boost your productivity at home, on the road, at the office, or in the classroom.

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

Lucian Constantin

IDG News Service
Show Comments

Most Popular Reviews

Latest News Articles

Resources

PCW Evaluation Team

Azadeh Williams

HP OfficeJet Pro 8730

A smarter way to print for busy small business owners, combining speedy printing with scanning and copying, making it easier to produce high quality documents and images at a touch of a button.

Andrew Grant

HP OfficeJet Pro 8730

I've had a multifunction printer in the office going on 10 years now. It was a neat bit of kit back in the day -- print, copy, scan, fax -- when printing over WiFi felt a bit like magic. It’s seen better days though and an upgrade’s well overdue. This HP OfficeJet Pro 8730 looks like it ticks all the same boxes: print, copy, scan, and fax. (Really? Does anyone fax anything any more? I guess it's good to know the facility’s there, just in case.) Printing over WiFi is more-or- less standard these days.

Ed Dawson

HP OfficeJet Pro 8730

As a freelance writer who is always on the go, I like my technology to be both efficient and effective so I can do my job well. The HP OfficeJet Pro 8730 Inkjet Printer ticks all the boxes in terms of form factor, performance and user interface.

Michael Hargreaves

Windows 10 for Business / Dell XPS 13

I’d happily recommend this touchscreen laptop and Windows 10 as a great way to get serious work done at a desk or on the road.

Aysha Strobbe

Windows 10 / HP Spectre x360

Ultimately, I think the Windows 10 environment is excellent for me as it caters for so many different uses. The inclusion of the Xbox app is also great for when you need some downtime too!

Mark Escubio

Windows 10 / Lenovo Yoga 910

For me, the Xbox Play Anywhere is a great new feature as it allows you to play your current Xbox games with higher resolutions and better graphics without forking out extra cash for another copy. Although available titles are still scarce, but I’m sure it will grow in time.

Featured Content

Latest Jobs

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?