Vulnerability Note VU#139931

Microsoft SQLXML HTTP components vulnerable to cross-site scripting via root parameter

Overview

A cross-site scripting vulnerability exists in the Microsoft SQLXML HTTP components. This vulnerability could allow an attacker to execute script on a victim's system with the victim's privileges.

I. Description

Microsoft SQL Server 2000 includes a feature called SQLXML that allows the server to handle SQL queries and responses via XML. IIS enables XML over HTTP using the SQLXML HTTP components. A client SQLXML HTTP request takes the form of a URI that contains a number of arguments including the name of the IIS server, the virtual directory (virtual root), and optional parameters. One of the optional parameters, root, wraps top-level XML tags around the response to the client, ensuring that the response is properly formed XML. The entire URI, including the root parameter, can be controlled by the client, or in the case of cross-site scripting, a third-party attacker.

The SQLXML HTTP components do not adequately validate the value of the root parameter. As a result, script or HTML included in a URI as part of the value of the root parameter will be executed by the web browser that accesses that URI.

Microsoft Security Bulletin MS02-030 notes that SQLXML is installed but disabled by default. An IIS server is only vulnerable if SQLXML is enabled and configured to run over HTTP.

For more information about cross-site scripting, see CERT Advisory CA-2000-02, the Malicious Web Scripts FAQ, and Cross-Site Scripting Vulnerabilities.

II. Impact

An attacker who can convince a user to access a URI supplied by the attacker could cause script or HTML of the attacker's choice to be executed in the user's browser. Using this technique, an attacker may be able to take actions with the privileges of the user who accessed the URI, such as issuing queries on the underlying SQL databases and viewing the results.

In the case of Microsoft Internet Explorer, malicious script or HTML will be executed in the same zone as the vulnerable IIS server. Typically, the Local intranet and Trusted sites zones in which an SQLXML-enabled IIS server is likely to exist are less restrictive, thus allowing an attacker to bypass Internet zone security settings.

III. Solution

Apply a Patch

Apply the appropriate patch as referenced in Microsoft Security Bulletin MS02-030.

Disable Scripting

To defend against cross-site scripting attacks from the client's perspective, disable scripting in your web browser and HTML-enabled email client. The zones feature of Microsoft Internet Explorer provides a way to selectively enable scripting for trusted sites. Instructions for disabling scripting can be found in the CERT/CC Malicious Web Scripts FAQ.

Systems Affected

Vendor	Status	Date Notified	Date Updated
Microsoft Corporation	Vulnerable	24-Jun-2002

References

VU#811371
http://www.cert.org/advisories/CA-2000-02.html
http://www.cert.org/tech_tips/malicious_code_FAQ.html
http://www.cert.org/archive/pdf/cross_site_scripting.pdf
http://www.westpoint.ltd.uk/advisories/wp-02-0007.txt
http://www.microsoft.com/technet/security/bulletin/MS02-030.asp
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/xmlref/xmlref_7583.asp
http://www.securityfocus.com/bid/5005

Credit

The CERT/CC thanks both Matt Moore of Westpoint and Microsoft for information used in this document.

This document was written by Art Manion.

Other Information

Date Public:	2002-06-12
Date First Published:	2002-06-25
Date Last Updated:	2002-08-08
CERT Advisory:	CA-2000-02
CVE-ID(s):	CAN-2002-0187
NVD-ID(s):	CAN-2002-0187
US-CERT Technical Alerts:
Metric:	8.95
Document Revision:	36

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