Adobe patches in-the-wild PDF bug, mum on details

Reader, Acrobat updates also block new 'no-click' exploits

Adobe Systems Inc. today patched a critical vulnerability in its PDF viewing and editing software that hackers have been exploiting for more than two months.

The update to Adobe Reader 9 and Adobe Acrobat 9 was released Tuesday afternoon, a day shy of the company's self-imposed deadline.

"Today, we posted the Adobe Reader 9.1 and Acrobat 9.1 update, which resolves the recent JBIG2 security issue, including the 'no-click' variant of the vulnerability," David Lenoe, Adobe's security program manager, said in a post to a company blog.

Lenoe's mention of no-click referred to newer exploits that do not rely on a user actually opening a malformed PDF file. Last week, for example, Belgian researcher Didier Stevens demonstrated that the vulnerability could be triggered simply by sending someone a malicious PDF document, and leveraging Windows Explorer's ability to "read" the file automatically to display such things as its title. Today, US-CERT also warned that the Windows Indexing Service can be abused to trigger the bug without any help from the user. "Exploitation using this technique also requires little to no user interaction," US-CERT said.

Adobe posted only the most general information in the accompanying security advisory it issued. "This vulnerability would cause the application to crash and could potentially allow an attacker to take control of the affected system," it read. "This issue is remotely exploitable. There are reports that this issue is being exploited."

More details may be available no later than March 25, when Adobe plans to patch the Linux and Solaris versions of the software. It will update the older Versions 7 and 8 of Reader and Acrobat for Windows and Mac by March 18.

According to Adobe, it first knew of the vulnerability on Jan. 16 when an unnamed partner provided it with an exploit snared in the wild. Other sources, however, have maintained that attackers had been actively exploiting the bug since Jan. 9, perhaps earlier.

On Feb. 12, Symantec Corp. handed Adobe another exploit sample, and posted some information about the flaw, but Adobe didn't acknowledge the problem until Feb. 19, when it issued a preliminary advisory. That delay, along with the several weeks it said it needed to craft a patch, was criticized by some security researchers.

That didn't stop today, as Adobe's release coincided with Microsoft Corp.'s monthly security update.

"People [at enterprises] will be scrambling because everyone was expecting this tomorrow," said Andrew Storms, director of security operations at nCircle Network Security Inc. "Today Microsoft, tomorrow Adobe. The problem from my standpoint is that this is a highly critical bug, but because it was released today, it will get lost in the noise."

"We didn't want users to be at risk any longer than necessary," countered Brad Arkin, Adobe's director for product security and privacy, who added that Adobe was able to push up its schedule by several hours to get the fix out today. "We understand how this might affect some users, but the alternative of waiting just didn't make any sense."

Links to the Windows and Mac versions of Reader 9.1 and Acrobat 9.1 have been posted on Adobe's site.

Copyright © 2009 IDG Communications, Inc.

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