Microsoft on Tuesday issued updates that plug a total of 49 security holes in Windows, Internet Explorer, and other software, the largest number of bugs ever to be fixed in a single Redmond Patch Tuesday release.
Microsoft classified six of the 49 vulnerabilities as critical, a severity rating that's generally reserved for bugs that allow adversaries to remotely execute malware on a Windows machine with little or no interaction needed by the user. Several other bugs, however, also make it possible to run code of an attacker's choosing, including flaws in the Windows common control library and the Microsoft foundation class library.
Those flaws carried lesser ratings because they can be exploited only when third-party browsers and file-archiving programs are used. Users who fall into these categories may want to give the vulnerabilities a higher severity rating, Microsoft said. What's more, 35 of the flaws could give attackers the means to run malicious code on victim's machines, antivirus provider Symantec said.
Ten of the vulnerabilities reside in IE, with two of them rated as critical. That gives rise to drive-by attacks in which victims are infected by doing nothing more than visiting a booby-trapped website. The elevated threat applies to IE versions 7 and 8 running on Windows Vista and Windows 7 even though those platforms have been designed to lessen the affect of such exploits.
Another update fixes a privilege-escalation vulnerability in Windows XP that was exploited by the Stuxnet worm, which researchers believe may have been unleashed to disrupt Iran's nuclear program. The malware spread by exploiting a total of four previously unpatched Windows vulnerabilities. With Tuesday's release, three of those vulns have been patched and a fourth — which also allows attackers to escalate limited system privileges — will be plugged in a future update, Microsoft said.
According to McAfee, the 49 vulnerabilities fixed on Tuesday shatter a previous record of 34, which was set in October 2009 and then tied in June and August.
Other Microsoft software that's affected includes the .NET foundation and Office. As usual, SANS has a helpful summary of all the updates, which is here. ®