Microsoft has produced a new patch to fix three critical vulnerabilities in its Microsoft VM, a virtual machine for the Win32 operating environment, the most serious of which could enable an attacker to gain complete control over a user’s system.
The Microsoft VM itself is a virtual machine for the Win32 operating environment. The Microsoft VM shipped in most versions of Windows, as well as in most versions of Internet Explorer, and was also available for some time as a separate download.
The first vulnerability involves the Java Database Connectivity (JDBC) classes, which provide features that allow Java applications to connect to and use data from a wide variety of data sources, ranging from flat files to SQL Server databases. The vulnerability results because of a flaw in the way the classes vet a request to load and execute a DLL on the user’s system. Although the classes do perform checks that are designed to ensure that only authorized applets can levy such a request, it’s possible to spoof this check by malforming the request in a particular way, thereby enabling an attacker to load and execute any DLL on the user’s system.
The second vulnerability also involves the JDBC classes, and occurs because certain functions in the classes don’t correctly validate handles that are provided as input. One straightforward use of this flaw would involve supplying invalid data in lieu of an actual handle when calling such a function. Microsoft has confirmed that this scenario would cause Internet Explorer to fail. In addition, there is at least a theoretical possibility that the flaw also could enable an attacker to provide data that would have the effect of running code in the security context of the user.
The third vulnerability involves a class that provides support for the use of XML by Java applications. This class exposes a number of methods; some of these are suitable for use by any applet, while others are only suitable for use by trusted ones. However, the class does not differentiate correctly between these cases, and instead makes all of the methods available to all applets. Among the functions that could be misused through this vulnerability are ones that would enable an applet to take virtually any desired action on the user’s system.
Versions of the Microsoft virtual machine are identified by build numbers. All builds of the Microsoft VM up to and including build 5.0.3805 are affected by these vulnerabilities.
More details can be found at: