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Title: Flaw in ISA Server Error Pages Could Allow Cross-Site
Scripting Attack (816456)
Date: 16 July 2003
Software: Microsoft(r) ISA Server
Max Risk: Important Bulletin: MS03-028
Microsoft encourages customers to review the Security Bulletins
at: http://www.microsoft.com/technet/security/bulletin/MS03-028.asp http://www.microsoft.com/security/security_bulletins/ms03-028.asp
ISA Server contains a number of HTML-based error pages that allow the server to respond to a client requesting a Web resource with a customized error. A cross-site scripting vulnerability exists in many of these error pages that are returned by ISA Server under specific error conditions.
To exploit this flaw, an attacker would have to first be aware of a specific ISA server and its access policies or host an ISA server of their own and create specific access policies designed to exploit this vulnerability. The attacker could then craft a request to trigger a page refusal. Once the attack was crafted, the attacker would have to host a Web site containing the link, or send the link to the user in the form of an HTML e-mail. After the user previewed or opened the e-mail, the malicious site could be visited automatically without further user interaction. In the Web-based attack scenario, an attacker would have no way to force a user to visit the Web site.
The vulnerability could only be exploited if the attacker could entice another user into visiting a Web page and clicking a link on it, or opening an HTML-based e-mail.
The request must be one that would cause the ISA server to respond with one of several affected error pages.
The vulnerability would not normally enable an attacker to gain any privileges on an affected ISA Server computer, breach the firewall, or compromise any cached content, unless the user is operating on the ISA server itself and is using the Web Proxy service to access the Internet.
for information on obtaining this patch.
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