Two New Windows Metafile Bugs Found

Just days after Microsoft patched a critical vulnerability in the way the Windows operating system renders certain types of graphics files, a hacker has published details of two new flaws that affect the same part of the operating system.

The new vulnerabilities were posted to the Bugtraq security mailing list today by a hacker using the name "cocoruder."

All Three Affect WMF Format

All three flaws concern the way Windows renders images in the Windows Metafile (WMF) format used by some CAD (computer-aided design) applications, but these latest flaws are far less serious than the vulnerability that Microsoft patched last week, according to security experts. That vulnerability was serious enough to cause Microsoft to take the unusual step of releasing an early patch for the problem, ahead of its monthly security software update.

Whereas the patched flaw was being exploited by attackers to take control of Windows machines, the latest vulnerabilities appear to pose the risk of simply crashing the WMF-viewing software, typically Internet Explorer. However, the bad guys would first need to trick a victim into viewing a specially crafted WMF image in order for this to happen, security experts say.

The vulnerabilities can be found in a number of versions of Windows, including Windows XP, Service Pack 2; Windows Server 2003, Service Pack 1; and Windows 2000, Service Pack 4, according to cocoruder's Bugtraq posting.

Not Major Flaws?

Because of the inherent complexity of image formats, attackers have plenty of opportunities to find bugs similar to the two that were revealed Monday, says Russ Cooper, senior information security analyst for Cybertrust.

Cooper says that the new WMF vulnerabilities are not a major cause for concern. "New malformed images that simply crash things aren't really that important unless they can be shown to cause code to execute," he said via instant message. "This is only getting any attention because it's WMF and Microsoft just released a WMF patch."

Johannes Ullrich, chief research officer for the SANS Institute, agrees that these types of image problems are fairly common, but he says that the fact that so many WMF vulnerabilities have popped up of late--Microsoft fixed three other WMF bugs in November--indicates that the software vendor could be doing a better job of predicting where its security problems might lie.

Microsoft should have been able to catch these latest flaws and fix them with its November patch, Ullrich says. "They really seem to have a problem thinking offensively," he says of Microsoft. "If you don't really look for these vulnerabilities with this offensive mindset, but if you instead look at it from a programmer's perspective...you just don't find a lot of these things."

"Every month they have one or two image problems they fix," Ullrich adds. "It's actually kind of surprising they don't get exploited more."