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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.