Microsoft issued 11 security bulletins today to wrap up the final Patch Tuesday of the year.
Of the 11, five have Microsoft's 'critical' rating. Those five plug security holes in Internet Explorer, Windows, Microsoft Exchange and GDI+, while the other six are rated 'important' and address flaws in Microsoft SharePoint, Windows, Office and Developer Tools.
Of the critical bulletins, perhaps the first one to apply is MS13-096, which fixes a bug in GDI+ that was publicly disclosed and has been the subject of targeted attacks.
"The zero-day vulnerability released just before last month’s Patch Tuesday is finally receiving a fix in MS13-096," said BeyondTrust CTO Marc Maiffret. "CVE-2013-3906 affects Windows Vista, Server 2008, Office 2003/2007/2010, and Lync 2010/2013. This was originally disclosed in an advisory in November, along with an accompanying Fix It solution. This vulnerability has been exploited successfully in targeted attacks and exploits for it exist within publicly available exploit frameworks. Patch this vulnerability as soon as you can."
Beyond MS13-096, Microsoft recommends prioritizing two other critical bulletins first and foremost: MS13-097 and MS13-099. MS13-097 addresses seven privately-reported vulnerabilities in Internet Explorer. The most serious of these vulnerabilities could allow remote code execution if a user views a specially-crafted webpage using Internet Explorer. An attacker who successfully exploited the most severe of these vulnerabilities could gain the same user rights as the current user, according to Microsoft.
MS13-099 patches a remote code execution vulnerability in the Microsoft Scripting Runtime Object Library.
"The vulnerability could allow remote code execution if an attacker convinces a user to visit a specially crafted website or a website that hosts specially crafted content," blogged Dustin Childs, group manager of response communications for Microsoft Trustworthy Computing. "An attacker who successfully exploited this vulnerability could gain the same user rights as the local user."
"In addition to the security bulletins, we are also releasing three security advisories this month and revising one more," he continued.
The security advisories include 2905247, which enables administrators to configure their ASP.NET servers to ensure that view state MAC remains enabled at all times and provides guidance on how to enable view state MAC on IIS servers. The other advisories are 2871690 and 2915720. The first of those notifies customers that an update is available for Windows 8 and Windows Server 2012 that revokes the digital signatures for specific Unified Extensible Firmware Interface modules. The latter informs customers of an impending change to how Windows verifies Authenticode-signed binaries, and recommends developers who sign binaries with Windows Authenticode ensure their signatures conform to the change by June 10, 2014.
"Finally, we are also revising Security Advisory 2755801 with the latest update for Adobe Flash Player in Internet Explorer," blogged Childs. "The update addresses the vulnerabilities described in Adobe Security bulletin APSB13-28."