Alert:Microsoft Security Bulletin - MS02-013
From: Russ (Russ.Cooper@RC.ON.CA)Date: 03/05/02
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Date: Mon, 4 Mar 2002 18:15:55 -0500 From: Russ <Russ.Cooper@RC.ON.CA> To: NTBUGTRAQ@LISTSERV.NTBUGTRAQ.COM
http://www.microsoft.com/technet/security/bulletin/MS02-013.asp
Java Applet Can Redirect Browser Traffic
Originally posted: March 04, 2002
Summary
Who should read this bulletin: Customers using Microsoft® Internet Explorer® in a configuration where a proxy server is interposed between the browser and the Internet.
Impact of vulnerability: Information Disclosure
Maximum Severity Rating: Critical
Recommendation: Customers using IE in a proxy server configuration as indicated above should immediately apply the patch.
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. The following builds of the Microsoft VM are affected:
- All builds of the Microsoft VM up to and including build 3802.
Technical description:
The Microsoft VM is a virtual machine for the Win32® operating environment. It runs atop Microsoft Windows® 95, Microsoft Windows 98, ME, Windows NT® 4.0 , Windows 2000® and Windows XP. It ships as part of Windows 98, ME, and Windows 2000 and also as part of Internet Explorer 5.5 and earlier.
The version of the Microsoft VM that ships with Internet Explorer version 4.x and 5.x contains a flaw affecting how Java requests for proxy resources are handled. A malicious Java applet could exploit this flaw to re-direct web traffic once it has left the proxy server to a destination of the attacker's choice.
An attacker could use this flaw to send a user's Internet session to a system of his own control, without the user being aware of this. The attacker could then forward the information on to the intended destination, giving the appearance that the session was behaving normally. The attacker could then send his own malicious response, making it seem to come from the intended destination, or could discard the session information, creating the impression of a denial of service. Additionally, the attacker could capture and save the user's session information. This could enable him to execute a replay attack or to search for sensitive information such as user names or passwords.
A system is only vulnerable if IE is used in conjunction with a proxy server. Users whose browsers are not behind a proxy server are not vulnerable to this vulnerability. However, those users would be vulnerable if they changed their browser to use a proxy server at a later date.
Mitigating factors:
- The vulnerability only affects configurations that utilize a proxy server. Customers who are not using a proxy server are not at risk from this vulnerability.
- Best practices strongly recommend using SSL to encrypt sensitive information such as user names, passwords and credit card numbers. If this has been done, sensitive information will be protected from examination and disclosure by an attacker exploiting this vulnerability.
Vulnerability identifier: CAN-2002-0058
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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