WEBsweeper/MIMEsweeper Executable File Content Check bypass Vulnerability Digital Armaments advisory is 12.15.2005 http://www.digitalarmaments.com/2005161283546323.html I. Background WEBsweeeper/MIMEsweeper is a commercial software that brings policy-based content security to the HTTP gateway. For many information or detail about the software you can refer to the vendor's homepage: http://www.mailsweeper.com/ II. Problem Description An attacker could trick a user to click on a mail link/attachment to download and run a malicious code (any malicious application in a .exe file). The ".exe" files should be filtered according to the security policies, but an attacker can trick to fail this test if the data sent to the webserver does not include the ".exe" extension. This problem persist on all platform where the data sent to a webserver (GET or POST) is fetched via a server side language (asp, php, etc..) that doesn't explicitly contain those regular expression. An example is: http://yourattack.server/asp?cmd=data&maliciouscodewithnumber&number=123 III. Detection This problem has been detected on latest version of WEBsweeper and MIMEsweeper actually avaiable and on prior version. It persist on all platforms. IV. Impact analisys Successful exploitation allow an attacker to easily trick a user to execute malicious code on his system. This attack bypass the protection offered by those content filter application. No exploit code is required. This attack can also be use in a massive way versus clients systems. V. Solution The vendor has given no response. First notification 12.15.2005. Second notification 12.19.2005. VI. Credit Oliver Muenchow - o.muenchow@netprotect.ch is credited with this discovery. Get paid and get stocks by vulnerabiliy submission http://www.digitalarmaments.com/contribute.html VII. Legal Notices Copyright © 2005 Digital Armaments LLC. Redistribution of this alert electronically is allowed. It should not be edited in any way. Reprint the whole is allowed, partial reprint is not permitted. For any other request please email customerservice@digitalarmaments.com for permission. Disclaimer: The information in the advisory is believed to be accurate at the time of publishing based on currently available information. Use of the information constitutes acceptance for use in an AS IS condition. There are no warranties with regard to this information. Neither the author nor the publisher accepts any liability for any direct, indirect, or consequential loss or damage arising from use of, or reliance on, this information.