Adobe admits PDF exploit, posts workaround

Expect Reader, Acrobat updates by end of the month to block Petkov's URI flaw

Adobe Systems has confirmed that there's a critical bug in its most popular programs, but it doesn't yet have a patch that protects Windows XP users against attacks arriving as PDF files.

In an advisory posted last week, Adobe admitted that the flaw first disclosed by Petko Petkov, a U.K.-based security researcher, was real. The company also provided a multiple-step work-around in lieu of a permanent fix to its Adobe Acrobat software and its free Adobe Reader application.

Last month, Petkov claimed in a blog posting that he had found a critical vulnerability that could be leveraged using PDF files, Adobe's popular document format. "Adobe Acrobat/Reader PDF documents can be used to compromise your Windows box," Petkov said. "Completely!!! Invisibly and unwillingly!!! All it takes is to open a PDF document or stumble across a page [that] embeds one."

At the time, Petkov declined to provide proof-of-concept code, telling users: "You have to take my word for it." He recommended steering clear of all PDFs until a fix was available.

Adobe's work-around requires editing the Windows registry, a daunting chore for most users, but it will protect against malicious PDF documents that exploit the "mailto:" URI (universal resource identifier) to trick users into downloading attack code. Mailto:, one of the most-frequently used URIs, launches the default e-mail client and opens a pre-address message when a link is clicked inside a Web browser.

The terse description indicates that the PDF vulnerability is yet another protocol-handling bug. Those flaws have been a hot topic in security circles since July, when another researcher, Norwegian Thor Larholm, showed how Internet Explorer and rival Firefox could be used to run malicious code by exploiting invalid URIs. In fact, the debate over patching responsibility resumed on Friday, when a German analyst said IE7 brought new bugs to Windows XP.

Juergen Schmidt of Heise Security specifically called out Adobe's software in a warning to a security mailing list, while Heise's Web site provided a proof-of-concept attack that used the mailto: URI to inject malicious code via a PDF. "This critical security problem is probably the same as recently detected and described by Petko Petkov," Heise said before Adobe published its advisory.

Adobe said it would update Adobe Reader 8.1 and Adobe Acrobat 8.1, as well as Adobe 3D, by the end of the month, but did not give a more specific date.

Microsoft, which has been criticized for not fixing the protocol-handing capabilities in Windows and Internet Explorer, has repeatedly said that the responsibility for making sure third-party software properly processes URIs such as mailto: falls to other vendors' application developers, not its engineers. In July, IE program manager Markellos Diorinos claimed that it would be "very difficult" for Windows to check for possibly invalid URIs.

If users cannot or will not use the work-around, Adobe's advice was essentially the same as Petkov's of two weeks ago. "Adobe recommends that Acrobat and Reader customers use caution when receiving unsolicited e-mail communications requesting user action, such as opening attachments or clicking Web links," the company said in its advisory.

Only Windows XP users running Internet Explorer 7 are at risk, Adobe said. Owners of Windows Vista, which sports its own version of IE 7, are safe from the mailto:-based attacks.

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.

Gregg Keizer

Computerworld (US)
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?