Microsoft Fixes Critical IE Security Vulnerabilities on Final Patch Tuesday for 2009

Microsoft issued patches for 12 security vulnerabilities Dec. 8 for its final Patch Tuesday of 2009, including a fix for a zero-day bug plaguing older versions of Internet Explorer.

All told Microsoft issued six security bulletins, three rated critical. The most serious of those is the Internet Explorer bulletin, which actually covers five security issues. In addition to having a critical rating, each of the issues addressed by the bulletin has an exploitability index rating of 1, meaning Microsoft considers it likely to be successfully attacked.

One of the vulnerabilities fixed in the IE bulletin is a zero-day flaw affecting Internet Explorer 6 and 7 first reported in November when proof-of-concept attack code surfaced.

"The highly critical vulnerability in IE6 [and] 7, with an exposure window to exploits of over three weeks without the availability of a patch, should put the task of getting users off IE6 [and] 7 on the top of IT admins' New Year's resolutions for 2010," Wolfgang Kandek, CTO of Qualys, told eWEEK. "They have to be migrated to a more modern browser, with the most viable options being IE 8 with its well-known patching mechanism or Firefox 3 with its more aggressive patching schedule."

Another critical bulletin addresses two vulnerabilities in Microsoft Windows that allow remote code execution if messages received by the Internet Authentication Service server are copied incorrectly into memory when handling PEAP (Protected Extensible Authentication Protocol) authentication attempts. The final critical bulletin resolves a vulnerability in editions of Microsoft Office Project 2000, 2002 and 2003 that could be exploited to execute code if a user opens a malicious Project file.

"MS09-074 is the least severe of the critical updates," opined Sheldon Malm, senior director of security strategy at Rapid7. "It is critical on Project 2000 and important on newer versions. While this should be prioritized and patched, I do not expect this one to see widespread activity."

His colleague Josh Abraham, a security researcher at Rapid7, added that MS09-071 is the month's second-most critical vulnerability.

"While CHAP (Challenge-Handshake Authentication Protocol) should not be overlooked, PEAP is the bigger issue," he said. "These exposures will be used in client-side wireless attacks and many enterprise customers are still not taking wireless security seriously enough."

The remaining bulletins are rated important, and affect Windows and WordPad and Office text converters. Barring an emergency out-of-band patch, the fixes cap a busy year for Microsoft on the security front. According to the company, it released a total of 74 bulletins in 2009 to address 189 vulnerabilities, compared with 78 bulletins addressing 155 vulnerabilities in 2008.