Microsoft patches critical Windows 7 bug, downplays exploit threat

Computerworld - Microsoft today delivered four security updates that patched four vulnerabilities in Windows, most of them affecting the newer editions of Vista and Windows 7.

Only one of the updates was marked "critical," Microsoft's most-serious threat ranking. Two of the remaining were labeled "important" and the fourth was tagged as "moderate."

As expected, Microsoft did not patch the Windows kernel vulnerability exploited by the Duqu campaign.

Top on Microsoft's chart today -- and on outside researchers' to-do lists as well -- was the MS10-083 update that patches a bug in Windows Vista's, Windows 7's and Server 2008's TCP/IP stack, which regulates Internet connections.

The vulnerability could be used by attackers in certain circumstances to hijack an unpatched PC, said Microsoft, which nevertheless downplayed the likelihood of successful attacks.

"This critical bug allows an attack via the network, and looks troublesome at first glance," said Andrew Storms, director of security operations at nCircle Security. "But it doesn't look very easy to pull off, so in this case, it's not as big a concern as one would think."

Storms pointed to a post by Microsoft engineers on the Security Research & Defense blog that spelled out the necessary conditions for an effective attack.

"We believe it is difficult to achieve [remote code execution] using this vulnerability considering that the type of network packets required are normally filtered at the perimeter and the small timing window ... and [that] a large number of packets are required to pull off the attack," wrote Ali Rahbar and Mark Wodrich of the Microsoft Security Response Center (MSRC).

Microsoft gave the vulnerability an exploitability index rating of "2," meaning that it expects only unreliable exploit code to appear in the next 30 days.

Even so, some researchers warned that if criminals focused their attention on the bug, they may be able to craft a consistent exploit that could be used to launch worm-based attacks.

Microsoft also updated Windows Mail and Windows Meeting Space on Vista, Windows 7 and Server 2008 to fix yet another "DLL load hijacking" vulnerability.

DLL load hijacking, sometimes called "binary pre-loading," describes a class of bugs first revealed in August 2010. Microsoft has been patching its software to fix the problem -- which can be exploited by tricking an application into loading a malicious file with the same name as a required dynamic link library, or DLL -- since last November.

Today's MS11-085 update was the eighteenth Microsoft has issued to fix DLL load-hijacking vulnerabilities in its software.

"They're a dime-a-dozen these days," said Storms of the latest in the long-running series.

Researchers also noted that while Microsoft did not patch the Duqu-exploited bug, it did fix a different flaw in the TrueType font parsing engine, the component targeted by the Trojan's attacks.