For June 2015 “Update Tuesday,” Microsoft released 8 security bulletins; only two the security updates are rated critical for resolving remote code execution (RCE) flaws, but two patches rated important also address RCE vulnerabilities.
Rated as Critical
MS15-056 is a cumulative security update for Internet Explorer, which fixes 24 vulnerabilities. Qualys CTO Wolfgang Kandek added, “This includes 20 critical flaws that can lead to RCE which an attacker would trigger through a malicious webpage. All versions of IE and Windows are affected. Patch this first and fast.”
Microsoft said the patch resolves vulnerabilities by “preventing browser histories from being accessed by a malicious site; adding additional permission validations to Internet Explorer; and modifying how Internet Explorer handles objects in memory.”
MS15-057 fixes a hole in Windows that could allow remote code execution if Windows Media Player opens specially crafted media content that is hosted on a malicious site. An attacker could exploit this vulnerability to “take complete control of an affected system remotely.”
Rated as Important
MS15-059 addresses RCE vulnerabilities in Microsoft Office. Although it’s rated important for Microsoft Office 2010 and 2013, Microsoft Office Compatibility Pack Service Pack 3 and Microsoft Office 2013 RT, Kandek said it should be your second patching priority. If an attacker could convince a user to open a malicious file with Word or any other Office tool, then he or she could take control of a user's machine. "The fact that one can achieve RCE, plus the ease with which an attacker can convince the target to open an attached file through social engineering, make this a high-risk vulnerability.”
MS15-060 resolves a vulnerability in Microsoft Windows “common controls.” The vulnerability “could allow remote code execution if a user clicks a specially crafted link, or a link to specially crafted content, and then invokes F12 Developer Tools in Internet Explorer.” Kandek explained, “MS15-060 is a vulnerability in the common controls of Windows which is accessible through Internet Explorer Developer Menu. An attack needs to trigger this menu to be successful. Turning off developer mode in Internet Explorer (why is it on by default?) is a listed work-around and is a good defense in depth measure that you should take a look at for your machines.”
The last four patches Microsoft issued address elevation of privilege vulnerabilities.
MS15-061 resolves bugs in Microsoft Windows kernel-mode drivers. “The most severe of these vulnerabilities could allow elevation of privilege if an attacker logs on to the system and runs a specially crafted application. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights.”
MS15-062 addresses a security hole in Microsoft Active Directory Federal Services. Microsoft said, “The vulnerability could allow elevation of privilege if an attacker submits a specially crafted URL to a target site. Due to the vulnerability, in specific situations specially crafted script is not properly sanitized, which subsequently could lead to an attacker-supplied script being run in the security context of a user who views the malicious content. For cross-site scripting attacks, this vulnerability requires that a user be visiting a compromised site for any malicious action to occur.”
MS15-063 is another patch for Windows kernel that could allow EoP “if an attacker places a malicious .dll file in a local directory on the machine or on a network share. An attacker would then have to wait for a user to run a program that can load a malicious .dll file, resulting in elevation of privilege. However, in all cases an attacker would have no way to force a user to visit such a network share or website.”
MS15-064 resolves vulnerabilities in Microsoft Exchange Server by “modifying how Exchange web applications manage same-origin policy; modifying how Exchange web applications manage user session authentication; and correcting how Exchange web applications sanitize HTML strings.”
It would be wise to patch Adobe Flash while you are at it as four of 13 vulnerabilities patched are rated critical.