Microsoft on Tuesday released 11 Security Bulletins addressing 26 vulnerabilities.
Though that's one fewer than Microsoft promised last week, Karthik Raman, a research scientist at McAfee, nonetheless called the release "a mammoth Patch Tuesday."
"It's going to be a pretty big month for a lot of companies," said Jason Miller, security data team manager for Shavlik.
Six of the bulletins are rated "critical" and five are rated "important." Counting vulnerabilities rather than bulletins, 17 of 26 are critical, the most since August 2006, according to Symantec.
MS08-041(critical) addresses a publicly disclosed vulnerability in the ActiveX control for the Snapshot Viewer in Microsoft Access (Microsoft Office 2003 and older).
MS08-042 (important) fixes a publicly disclosed vulnerability in Microsoft Word 2002 and 2003.
Both MS08-041 and MS08-042 are being actively used in cyberattacks, according to McAfee.
MS08-043 (critical for Excel 2000; important for more recent versions of Excel) patches four privately reported Microsoft Excel vulnerabilities.
MS08-045 (critical) resolves six Microsoft Internet Explorer vulnerabilities, five privately reported and one publicly disclosed.
MS08-046 (critical) repairs a privately reported vulnerability in the Microsoft Image Color Management system for Windows 2000, Windows XP, and Windows Server 2003.
Miller said that MS08-045 and MS08-046 should be patched as soon as possible. Using these vulnerabilities, "you could craft a malicious site and an unpatched browser could potentially get infected," he said.
MS08-047 (important) closes a privately reported information disclosure vulnerability in Windows Internet Protocol Security for Windows Vista and Windows Server 2008 following the importation of IPsec policies from Windows Server 2003 domains.
MS08-048 (important for Windows 2000, XP, and Vista; low for Windows Server 2003 and 2008) resolves a privately reported information disclosure vulnerability in Outlook Express and Windows Mail.
MS08-049 (important) addresses two privately reported code execution vulnerabilities in Microsoft Windows Event System. Local login is required to exploit the vulnerability. MS08-050 (important) fixes a publicly disclosed information disclosure vulnerability in Windows Messenger affecting Windows XP and Windows Server 2003. Windows Live Messenger is not affected. MS08-051 (critical for PowerPoint 2000; important for more recent versions of PowerPoint) fixes three privately reported vulnerabilities in Microsoft PowerPoint 2000, Microsoft PowerPoint 2002, Microsoft PowerPoint 2003, and the PowerPoint Viewer 2003.
In addition to this month's patch, Miller urged IT administrators to make sure that last month's Microsoft DNS patch has been applied. "That one's actively being exploited all over the place," he said.