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SurgeFTP 2.3a1 Denial of Service

Portcullis Security Advisory 06-061

Vulnerable System:


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.


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.


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 


The proof of concept exploit code is available.

Vendor Status:

Vendor notified. The vulnerability has been fixed.


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