Vulnerability Note VU#657625

Microsoft Virtual Machine incorrectly parses the domain portion of URLs containing a colon

Overview

Some versions of the Microsoft virtual machine (Microsoft VM) contain a flaw that could allow untrusted Java applets from an attacker's site to be run instead of the trusted applet from the intended site.

I. Description

The Microsoft virtual machine (Microsoft VM) enables Java programs to run on Windows platforms. The Microsoft VM is included in most versions of Windows and Internet Explorer.

The Microsoft VM contains a flaw that incorrectly parses URLs if they contain a colon used to indicate the port number. The vulnerability results because it's possible to create a URL that will cause the Microsoft VM to incorrectly determine the domain from which a Java applet was loaded, and conclude that it came from one web site when in fact it came from another. Specifically, if a URL is crafted in a particular format containing references to two different web sites, the VM will incorrectly process it and load a Java applet from an untrusted site while running it in the trusted site's domain.
The crafted URL could be hosted on an attacker's web site or introduced to the user via an HTML email.

II. Impact

Because the malicious applet would be located in the context of the legitimate site's domain, it could potentially access any cookies that the legitimate site had placed on the victim user's system. Additionally, any information the malicious applet solicited from the user could be relayed back to the attacker's site instead of the intended site.

III. Solution

Apply a patch from the vendor

Microsoft has issued Security Bulletin MS02-069 addressing this vulnerability. Users are encouraged to follow the instructions outlined in the bulletin and apply the patches that it refers to.

Workarounds

Disable Java

- if the ability to run Java applets is not required or desired, configure your web browser to not execute them. Information about disabling Java in various web browsers can be found here.

Note that disabling Java in your web browser may not mitigate this vulnerability for Java programs that are invoked via another method.

Systems Affected

Vendor	Status	Date Notified	Date Updated
Microsoft Corporation	Vulnerable	18-Dec-2002

References

http://www.iss.net/security_center/static/10579.php
http://www.securityfocus.com/bid/6142

Credit

Thanks to Jouko Pynnonen for reporting this vulnerability.

This document was written by Chad R Dougherty.

Other Information

Date Public:	2002-11-12
Date First Published:	2003-01-21
Date Last Updated:	2003-01-21
CERT Advisory:
CVE-ID(s):	CAN-2002-1286
NVD-ID(s):	CAN-2002-1286
US-CERT Technical Alerts:
Severity Metric:	7.36
Document Revision:	13

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