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CERT Coordination Center

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

Vulnerability Note VU#657625

Original Release Date: 2003-01-21 | Last Revised: 2003-01-21


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.


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.


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.


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.


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.

Vendor Information


Microsoft Corporation Affected

Notified:  November 26, 2002 Updated: December 18, 2002



Vendor Statement

Microsoft Corporation's statement can be found in Microsoft Security Bulletin MS02-069.

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.


The CERT/CC has no additional comments at this time.

If you have feedback, comments, or additional information about this vulnerability, please send us email.

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Thanks to Jouko Pynnonen for reporting this vulnerability.

This document was written by Chad R Dougherty.

Other Information

CVE IDs: CVE-2002-1286
Severity Metric: 7.36
Date Public: 2002-11-12
Date First Published: 2003-01-21
Date Last Updated: 2003-01-21 21:56 UTC
Document Revision: 14

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