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

Gregg Keizer

Computerworld (US)
Show Comments

Brand Post

Bitdefender 2018

With determination and drive, you achieve outstanding performance! Get Bitdefender Total Security 2018 Now!

Most Popular Reviews

Latest Articles

Resources

PCW Evaluation Team

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

Louise Coady

Brother MFC-L9570CDW Multifunction Printer

The printer was convenient, produced clear and vibrant images and was very easy to use

Edwina Hargreaves

WD My Cloud Home

I would recommend this device for families and small businesses who want one safe place to store all their important digital content and a way to easily share it with friends, family, business partners, or customers.

Walid Mikhael

Brother QL-820NWB Professional Label Printer

It’s easy to set up, it’s compact and quiet when printing and to top if off, the print quality is excellent. This is hands down the best printer I’ve used for printing labels.

Ben Ramsden

Sharp PN-40TC1 Huddle Board

Brainstorming, innovation, problem solving, and negotiation have all become much more productive and valuable if people can easily collaborate in real time with minimal friction.

Sarah Ieroianni

Brother QL-820NWB Professional Label Printer

The print quality also does not disappoint, it’s clear, bold, doesn’t smudge and the text is perfectly sized.

Featured Content

Product Launch Showcase

Latest Jobs

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?