Department of Homeland Security now offering same advice as a security professional

Firstly – if you want the no-nonsense run-down on this – visit this blog post from earlier – because the post you are on now – is EXTREMELY TECHNICAL…

Source article: http://www.kb.cert.org/vuls/id/625617

Overview

Java 7 Update 10 and earlier contain an unspecified vulnerability that can allow a remote, unauthenticated attacker to execute arbitrary code on a vulnerable system.

Description

The Oracle Java Runtime Environment (JRE) 1.7 allows users to run Java applications in a browser or as standalone programs. Oracle has made the JRE available for multiple operating systems. The Java JRE plug-in provides its own Security Manager. Typically, a web applet runs with a security manager provided by the browser or Java Web Start plugin. Oracle’s document states, “If there is a security manager already installed, this method first calls the security manager’s checkPermission method with a RuntimePermission("setSecurityManager") permission to ensure it’s safe to replace the existing security manager. This may result in throwing a SecurityException". By leveraging the a vulnerability in the Java Management Extensions (JMX) MBean components, unprivileged Java code can access restricted classes. By using that vulnerability in conjunction with a second vulnerability involving the Reflection API and the invokeWithArguments method of the MethodHandle class, an untrusted Java applet can escalate its privileges by calling the the setSecurityManager() function to allow full privileges, without requiring code signing. Oracle Java 7 update 10 and earlier are affected. This vulnerability is being attacked in the wild, and is reported to be incorporated into exploit kits. Exploit code for this vulnerability is also publicly available.

Impact

By convincing a user to visit a specially crafted HTML document, a remote attacker may be able to execute arbitrary code on a vulnerable system. Note that applications that use the Internet Explorer web content rendering components, such as Microsoft Office or Windows Desktop Search, may also be used as an attack vector for this vulnerability.

Solution

We are currently unaware of a practical solution to this problem. Please consider the following workarounds:

Disable Java in web browsers

Starting with Java 7 Update 10, it is possible to disable Java content in web browsers through the Java control panel applet. Please see the Java documentation for more details.
Note: Due to what appears to potentially be a bug in the Java installer, the Java Control Panel applet may be missing on some Windows systems. In such cases, the Java Control Panel applet may be launched by finding and executing javacpl.exe manually. This file is likely to be found in C:\Program Files\Java\jre7\bin or C:\Program Files (x86)\Java\jre7\bin.
Also note that we have encountered situations where Java will crash if it has been disabled in the web browser as described above and then subsequently re-enabled. Reinstalling Java appears to correct this situation.
System administrators wishing to deploy Java 7 Update 10 or later with the “Enable Java content in the browser” feature disabled can invoke the Java installer with the WEB_JAVA=0 command-line option. More details are available in the Java documentation.