New PDF Zero-Day Vulnerability

The British security researcher who has disclosed two critical flaws in popular media files in the past week said Thursday that a zero-day vulnerability in Adobe Inc.'s pervasive PDF files could be exploited to snatch control of Windows XP systems.

Petko Petkov, a penetration tester who disclosed a zero-day flaw in Apple Inc.'s QuickTime a week ago and a similarly critical bug in Microsoft Corp.'s Windows Media Player on Tuesday, now says that Adobe System Inc.'s Acrobat Reader files harbor a serious vulnerability.

The PDF zero-day beats the media file flaws hands down, said Petkov. "Adobe Acrobat/Reader PDF documents can be used to compromise your Windows box," he said on his blog Friday. "Completely!!! Invisibly and unwillingly!!! All it takes is to open a PDF document or stumble across a page, which embeds one."

In the QuickTime and Windows Media Player cases, Petkov posted proof-of-concept exploit code. Not so this time. He explained why he refused to publish code to prove that the PDF vulnerability is real.

"The issue is quite critical given the fact that PDF documents are in the core of today's modern business," Petkov wrote. "This and the fact that it may take a while for Adobe to fix their closed source product are the reasons why I am not going to publish any POCs [proof-of-concepts]. You have to take my word for it. The POCs will be released when an update is available."

Although Petkov provided no proof of his claim, Symantec Corp. was ready to believe. "Although these claims are currently unverifiable, this researcher has identified several vulnerabilities in the past and is likely credible regarding these findings," the company said in an alert to customers of its DeepSight threat network.

"My advise [sic] for you is not to open any PDF files (locally or remotely)," Petkov said. Petkov said he had tested and verified that the vulnerability exists in the most recent version of Acrobat Reader, Version 8.1, and can be exploited on PCs running Windows XP SP2.

The bug wouldn't be the first found in Adobe's popular PDF file format or the software that creates and displays them. In January, for example, Adobe updated Reader and Acrobat to Version 8.0 to eliminate a cross-site scripting vulnerability.

Adobe officials were not available for comment.