Microsoft on Tuesday patched for 15 vulnerabilities with the distribution of six bulletins, one of which the software giant recommends administrators immediately apply.
That fix, MS09-065, corrects three vulnerabilities in Windows kernel-mode drivers. One of the flaws is considered "critical," but does not impact Vista or Server 2008.
The bug, however, can be exploited on Windows 2000, XP and Server 2003 machines to execute remote code if a user views content rendered in a maliciously crafted Embedded OpenType font, used on web pages. Proof-of-concept code already is available to launch drive-by attacks, security researchers said Tuesday. And according to Microsoft, consistent exploit code is expected.
"We recommend customers prioritize and deploy this update immediately," Jerry Bryant, senior security program manager at Microsoft, wrote on the company's Security Response Center blog.
Ben Greenbaum, senior research manager at Symantec, agreed that the bulletin should be urgently deployed because the flaw is at the kernel level, meaning it does not matter with what privilege the user's machine is running.
"All that's required of a user to become infected by it is simply viewing a compromised web page," he said. "Symantec isn't seeing any active exploits of this in the wild yet, but we think attackers will be paying a lot of attention to it in the future."
Tuesday's update also includes two other "critical" bulletins, which address four vulnerabilities, and three "important" bulletins that take care of 10 bugs. One of those -- MS09-067 -- resolves eight flaws in Office that can lead to remote code execution if a user opens a specially crafted Excel file.
Sheldon Malm, senior director of security strategy at Rapid7, a vulnerability management provider, called MS09-067 a "sleeper threat" because Microsoft considers it highly exploitable and because Excel is widely used.