http://www.microsoft.com/technet/security/bulletin/MS02-052.asp

Flaw in Microsoft VM JDBC Classes Could Allow Code Execution (Q329077)

Originally posted: September 18, 2002

Summary

Who should read this bulletin: All customers using Microsoft® Windows®.

Impact of vulnerability: Three vulnerabilities, the most serious of which could enable an attacker to gain complete control over a user's system.

Maximum Severity Rating: Critical

Recommendation: Customers should apply the patch immediately.

Affected Software:
- Versions of the Microsoft virtual machine (Microsoft VM) are identified by build numbers, which can be determined using the JVIEW tool as discussed in the FAQ. All builds of the Microsoft VM up to and including build 5.0.3805 are affected by these vulnerabilities.

Technical description:

The Microsoft VM is a virtual machine for the Win32® operating environment. The Microsoft VM shipped in most versions of Windows (a complete list is available in the FAQ), as well as in most versions of Internet Explorer. It also was available for some time as a separate download. A new patch for the Microsoft VM is available, which eliminates three security vulnerabilities. The attack vectors for all of them would likely be the same. An attacker would likely create a web page that, when opened, exploits the desired vulnerability, and either host it on a web page or send it to a user as an HTML mail.

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.

Mitigating factors:
- In order to exploit any of these vulnerabilities via the web-based attack vector, the attacker would need to entice a user into visiting a web site that the attacker controlled. The vulnerabilities themselves provide no way to force a user to a web site.
- Java applets are disabled within the Restricted Sites Zone. As a result, any mail client that opened HTML mail within the Restricted Sites Zone, such as Outlook 2002, Outlook Express 6, or Outlook 98 or 2000 when used in conjunction with the Outlook Email Security Update, would not be at risk from the mail-based attack vector.
- The vulnerability would gain only the privileges of the user, so customers who operate with less than administrative privileges would be at less risk from the vulnerability.
- Corporate IT administrators could limit the risk posed to their users by using application filters at the firewall to inspect and block mobile code.

Vulnerability identifier:
- DLL execution via JDBC classes: CVE-CAN-2002-0866
- Handle validation flaw: CVE-CAN-2002-0867
- Inappropriate methods exposed in XML support classes: CVE-CAN-2002-0865

This email is sent to NTBugtraq automatically as a service to my subscribers. Since its programmatically created, and since its been a long time since anyone paid actual money for my programming skills, it may or may not look that good...;-]

I can only hope that the information it does contain can be read well enough to serve its purpose.

Cheers,
Russ - Surgeon General of TruSecure Corporation/NTBugtraq Editor

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