Portcullis Security Advisory 06-061




Vulnerable System:

SurgeFTP


Vulnerability Title:

The mirror mechanism allows Denial of Service.


Vulnerability discovery and development:

Portcullis Security Testing Services discovered this vulnerability.  
Further research was then carried out.


Credit for Discovery:

Nico Leidecker - Portcullis Computer Security Ltd.


Affected systems: 

Version 2.3a1 Linux and is likely to affect other platforms.


Details:

SurgeFTP provides a mirror functionality but fails to detect malformated 
command responses.  This concerns the PASV command and its response from the 
mirrored server. SurgeFTP fails to parse a response to PASV properly so that
it will crash if the response was malformated.


Impact:

It may be possible for an attacker to shut down the service. By default, 
SurgeFTP respawns after a couple of seconds. But then, immediately reconnects 
to the mirrored server. As long as the attacker keeps sending malformated 
PASV responses to the server, it will keep shutting down immediately after 
restarting.


Exploit:

The proof of concept exploit code is available.


Vendor Status:

Vendor notified. The vulnerability has been fixed.


Copyright: 

Copyright © Portcullis Computer Security Limited 2005, All rights reserved 
worldwide. 

Permission is hereby granted for the electronic redistribution of this 
information. It is not to be edited or altered in any way without the express 
written consent of Portcullis Computer Security Limited.


Disclaimer:

The information herein contained may change without notice. Use of this 
information constitutes acceptance for use in an AS IS condition. There are NO 
warranties, implied or otherwise, with regard to this information or its use. 
Any use of this information is at the user's risk. In no event shall the 
author/distributor (Portcullis Computer Security Limited) be held liable for 
any damages whatsoever arising out of or in connection with the use or spread 
of this information.