Five of the eight patches are designated "critical."
The most significant aspect of this month's patches, said Andrew Storms, director of security operations at nCircle Network Security, is that Microsoft has fixed three of the four publicly known vulnerabilities in its software.
This includes an Excel flaw that Microsoft warned about in February, an Internet Information Services and SQL Server vulnerability that Microsoft acknowledged about in April 2008, and a WordPad Text Converter that Microsoft disclosed in December.
Not addressed in the April crop of patches is a PowerPoint flaw, documented in a security advisory earlier this month.
Storms said that while none of the vulnerabilities could give rise to malware as contagious as the Conficker worm, administrators should nonetheless patch as quickly as possible.
He characterized the amount of work required to patch corporate systems as fairly heavy because Oracle also is releasing its quarterly software patches Tuesday. "The two combined will make for a pretty sleepless week," he said.
The bulletins are:
- MS09-009 (Critical): This update resolves a newly discovered, privately reported, and publicly disclosed vulnerability in Microsoft Excel.
- MS09-010 (Critical): This update resolves two publicly disclosed vulnerabilities and two privately reported vulnerabilities in Microsoft WordPad and Microsoft Office Text Converters.
- MS09-011 (Critical): This update resolves a newly discovered and privately reported vulnerability in Microsoft DirectX.
- MS09-012 (Important): This update resolves four publicly disclosed vulnerabilities in Microsoft Windows.
- MS09-013 (Critical): This update resolves one publicly disclosed vulnerability and two privately reported vulnerabilities in Microsoft Windows HTTP Services.
- MS09-014 (Critical): This update resolves four privately reported vulnerabilities and two publicly disclosed vulnerabilities in Internet Explorer.
- MS09-015 (Moderate): This update resolves one publicly disclosed vulnerability in the Windows SearchPath function.
- MS09-016 (Important): This update resolves a privately reported vulnerability and a publicly disclosed vulnerability in Microsoft Internet Security and Acceleration Server and Microsoft Forefront Threat Management Gateway, Medium Business Edition.
In an e-mailed statement, Symantec senior research manager Ben Greenbaum said that the memory corruption vulnerability (CVE-2009-0554) fixed with the MS09-014 patch looks to be the easiest to exploit. It could allow an attacker to compromise a victim's computer merely by enticing the victim to view a Web site with malicious content.
"Many browser vulnerabilities, such as these announced by Microsoft, allow attackers to gain complete control over everything a user has permission to do on an exploited machine," said Greenbaum. "You can imagine how dangerous this can be, especially if the user has administrator rights."
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