Microsoft fixed 23 vulnerabilities across eight security bulletins as part of its October Patch Tuesday release.
October's Patch Tuesday release resolved issues in Internet Explorer versions 6 through 9, all versions of Microsoft Windows from XP through 7, .NET and Silverlight, Microsoft Forefront Unified Access Gateway and Host Integration Server, Microsoft said Oct. 11. Two of the patches are rated "critical," and six are rated "important," Microsoft said.
Microsoft recommended that organizations apply the Internet Explorer and .NET/Silverlight patches first as attackers are likely to come out with a reliable exploit within 30 days. Malware developers often reverse-engineer the patches after they are released to develop exploits that target unpatched systems.
Kaspersky Lab senior security researcher Kurt Baumgertner said that reliable exploitation will lead to remote code execution across a wide variety of Windows versions because Internet Explorer and Silverlight are heavily used software clients.
"It would be surprising to not see related exploits added to packs and widely used in attack attempts over the coming months," Baumgartner wrote on the Securelist blog.
The critical update for Internet Explorer fixed at least eight known security flaws in all versions of Microsoft's Web browser, including the latest Internet Explorer 9. The bugs were in the way IE handled objects in memory and the way memory was allocated and accessed.
If exploited, the bugs in Internet Explorer would expose the user to drive-by download attacks just by merely browsing to a booby-trapped site, according to Microsoft. The attacker can gain the same user rights as the user, but users who have accounts with fewer user rights are likely to be less impacted than those who have administrative rights.
"Patching browsers will be top priority because the vulnerabilities fixed with each security bulletin release in browsers are top exploit targets for attackers," Jason Miller, manager of research and development at VMware, told eWEEK.
The second critical update fixed a remote code execution flaw in .NET Framework and Silverlight. Users could be compromised just by viewing a malicious page specifically running XAML Browser Applications or Silverlight applications, Microsoft said. The vulnerability would also allow remote code execution on a server running IIS if that system allowed processing ASP.NET pages and specially crafted ASP.NET pages are uploaded to the server and executed. The .NET issue also affects Mac OS clients, according to Dave Marcus, director of security research and communications at McAfee Labs.
The .NET framework class inheritance vulnerability is "complex to exploit" but can be exploited in a "number of ways," including traditional downloads, drive-by-downloads and by hosting a malicious .NET application, said Joshua Talbot, security intelligence manager at Symantec Security Response.
Microsoft fixed five privately reported vulnerabilities in Microsoft Forefront Unified Access Gateway. The cross-site scripting vulnerability in Microsoft Forefront, if exploited, will allow attackers to steal log-in credentials used for VPN access and gain access to sensitive data. The patch for Microsoft Forefront will likely affect the "smallest number" of organizations because Microsoft generally doesn't have a big presence in corporate security infrastructure, Marcus Carey, a security researcher at Rapid7, told eWEEK.
Microsoft has two bulletins to fix the DLL preload vulnerabilities in Windows Media Center and Microsoft Active Accessibility. Microsoft has released a patch 17 times to close this issue in various programs since it was first identified Aug. 23, 2010, according to Miller.
"Overall this Patch Tuesday is fairly moderate. Three of the included vulnerabilities have been previously disclosed, and there is an available proof-of-concept code," Marcus said.
October is often the last month in which administrators at financial and retail organizations apply patches before going into "lock-down" mode for the holiday shopping season, according to Andrew Storms, director of security operations at nCircle. "Enterprise IT teams should get ready to pull out all the stops," Storms said.