Office exploit hits the street

Attack code that targets a recently patched vulnerability in Microsoft's Office suite has gone public, a security company said Monday as it urged users to update immediately.

The exploit, which was posted yesterday to the milw0rm.com Web site, takes advantage of one of two flaws fixed by Microsoft in its MS08-016 security update. Microsoft issued the update March 11 as part of a four-bulletin batch.

"The exploit that is currently available uses a PowerPoint file to leverage the vulnerability on Office XP SP3," said Symantec analyst Anthony Roe in an alert to customers of the company's DeepSight threat network. "The payload is designed to execute the 'calc.exe' calculator program on Windows, however, it will not be difficult to modify this exploit to add a malicious payload."

According to Roe, the rigged PowerPoint file triggers the "Microsoft Office File Memory Corruption Vulnerability," one of two vulnerabilities addressed by MS08-016. Microsoft said earlier this month that the flaw rated a "critical" label for users of Office 2000, and "important" for Office XP and Office 2003 on Windows machines, and Office 2004 for Mac. However, the company acknowledged that if successful, an attack against any of the four versions could result in the attacker wresting control of the machine from its rightful owner.

Microsoft spelled out two possible attack vectors: enticing users to a malicious Web site that hosts a specially rigged file or feeding users malformed files as e-mail attachments.

"Customers are strongly advised to install the patches from the bulletin MS08-016 if they are not installed already, especially considering the availability of this exploit," said Roe.

Computerworld is an InfoWorld affiliate.