Microsoft Internet Explorer (IE) does not properly determine the source of script used in URLs. An attacker could exploit this vulnerability to evaluate script in different security domains. By causing script to be evaluated in the Local Machine Zone, the attacker could execute arbitrary code with the privileges of the user running IE.
IE uses a cross-domain security model to maintain separation between browser frames from different sources. This model is designed to prevent code in one domain from accessing data in a different domain. From Microsoft Security Bulletin MS03-048:
One of the principal security functions of a browser is to ensure that browser windows that are under the control of different Web sites cannot interfere with each other or access each other's data, while allowing windows from the same site to interact with each other. To differentiate between cooperative and uncooperative browser windows, the concept of a "domain" has been created. A domain is a security boundary - any open windows within the same domain can interact with each other, but windows from different domains cannot. The cross-domain security model is the part of the security architecture that keeps windows from different domains from interfering with each other.
This URL will display an alert dialog with the contents of the HTTP cookie for the current site:
It is possible that vbscript: protocol URLs are similarly affected.
An attacker could exploit this vulnerability using a crafted HTML document containing script. The IE DHTML Object Model supports references to specific frames using the TARGET attribute (or property). Using known TARGET values such as _search or _media, an attacker can cause arbitrary HTML (including script) to be evaluated in the Local Machine Zone. Also, due to the way IE determines the MIME type of a file referenced by a URL, an HTML document may not necessarily have the expected file name extension (.html or .htm). There have been several public incident reports of systems being compromised via this vulnerability.
Any program that uses the WebBrowser ActiveX control or the IE HTML rendering engine (MSHTML) may be affected by this vulnerability. Outlook and Outlook Express are affected; however, recent versions of these programs open mail in the Restricted Sites Zone where ActiveX controls and Active scripting are disabled by default.
This vulnerability is referenced in MS03-048 as the Script URLs Cross Domain Vulnerability (CAN-2003-0816).
By convincing a victim to view an HTML document (web page, HTML email), an attacker could evaluate script in a different security domain than the one containing the attacker's document. By causing script to be evaluated in the Local Machine Zone, the attacker could execute arbitrary code with the privileges of the user running IE. The attacker could also read or modify data in other web sites (read cookies/content, modify/create content, etc.).
A number of variations of this vulnerability were publicly reported by Liu Die Yu. Thanks to Microsoft and Thor Larholm for information used in this document.
This document was written by Art Manion.
|Date First Published:||2003-11-18|
|Date Last Updated:||2004-04-02 16:26 UTC|