Frame Domain Verification, Unauthorized Cookie Access and Malformed Component Attribute Vulnerabilities

Three security vulnerabilities exist in Internet Explorer 4 and 5 which could allow a malicious web site operator to read files and cookies or to run code of his choice on the computer of a visiting user.

Issue

"Frame Domain Verification" Vulnerability
When a web server opens a frame within a window, the IE security model should only allow the parent window to access the data in the frame if they are in the same domain. However, two functions available in IE do not properly perform domain checking, with the result that the parent window could open a frame that contains a file on the local computer, then read it. This could allow a malicious web site operator to view files on the computer of a visiting user. The web site operator would need to know (or guess) the name and location of the file, and could only view file types that can be opened in a browser window.

"Unauthorized Cookie Access" Vulnerability
By design, the IE security model restricts cookies so that they can be read only by sites within the originator's domain. However, by using a specially-malformed URL, it is possible for a malicious web site operator to gain access to another site's cookie and read, add or change them. A malicious web site operator would need to entice a visiting user into clicking a link in order to access each cookie, and could not obtain a listing of the cookies available on the visitor's system. Even after recovering a cookie, the type and amount of personal information would depend on the privacy practices followed by the site that place it there.

"Malformed Component Attribute" Vulnerability
The code used to invoke ActiveX components in IE has an unchecked buffer and could be exploited by a malicious web site operator to run code on the computer of a visiting user. The unchecked buffer is only exposed when certain attributes are specified in conjunction with each other.

Affected Products

• Microsoft Internet Explorer 4.0, 4.01, 5.0 & 5.01

Download

Patch: http://www.microsoft.com/windows/ie/download/critical/patch11.htm

Further Details

Source: Microsoft Corporation

Updated: August 9, 2000

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