First discovered by Google’s Project Zero several months ago, a vulnerability in Adobe Reader makes it possible for malicious code to break out of the program’s sandbox and execute arbitrary instructions. According to ZDNet, the problem affects version 11.0.8 of Acrobat and Reader and was given a severity rating of 10 by the U.S. Computer Emergency Readiness Team. Now, Google is making the details of its findings public, and some users are unsure whether Adobe has done enough to fix the problem.

Adobe Reader a Big Target

Adobe owns popular software. Acrobat, Reader and Flash are used for countless business and personal applications every day, and surfing the Web and accessing documents is nearly impossible without these technologies.

As a result, Adobe and its code are high-profile targets for cybercriminals, and the company is no stranger to attacks. In 2013, McAfee discovered a flaw in Reader that allowed individuals to track the usage of a PDF.

Meanwhile, Wired recently reported on a new malware group called DarkHotel that used a fake Adobe Flash update to infect wireless network users in high-end hotels. Therefore, reports of a new Adobe Reader bug aren’t surprising, but this one may pose a more serious threat than other recent issues — and, more importantly, may not be entirely corrected.

Found It

Google’s Project Zero was the first to find this exploit and report it to Adobe, according to Threatpost. It revolves around the handling of the MoveFileEx call hook. There is a “timing race” that happens when the MoveFileEx function is resolving the location of the file source and the destination to ensure that they are within policy guidelines. A sandboxed process using an oplock can get there first, then waits for MoveFileEx to open the original file for moving.

“This allows code in the sandbox to write an arbitrary file to the file system,” James Forshaw of Project Zero told Threatpost.

It is no surprise, then, that Google had to bring this to Adobe’s attention, and Adobe dealt with it — sort of. Following the bug report, the company upgraded Reader and Acrobat to Version 11.0.9, which made it “difficult, if not impossible,” for malicious actors to use this vulnerability, according to a Google report. The bottom line? This wasn’t a patch for this specific problem, and therefore, the fix doesn’t eliminate the race condition. It just makes it much more difficult for cybercriminals to win.

Out in the Open

So why is this coming to light months after the issue was identified? According to Project Zero policy, vulnerabilities are first reported to companies that own the software, giving them the chance to fix the problem without media attention and the possibility of a copycat attack. After 90 days, however, Project Zero publishes its findings along with proof-of-concept documentation. This makes sense because users have a right to know about problems in their software, while companies get the chance to fix issues before they become public knowledge.

With the Reader vulnerability now out in the wild, the effectiveness of Adobe’s solution will be put to the test. Users should update to the latest version of Adobe Reader and Acrobat but keep an ear to the ground. Adobe’s products are big game, and when it comes to hunting cybercriminals, “difficult but not impossible” is often doublespeak for “takes a little more time.”

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