WzdFTPD < 8.1 Denial of service

[S21sec Labs <labs () s21sec com>]

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                     - S21Sec Advisory -

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    Title:   WzdFTPD Denial of Service
       ID:   S21SEC-033-en
 Severity:   Medium - Denial of Service
  History:   26.Dic.2006 Vulnerability discovered
                     8.Ene.2007 Vendor contacted

    Scope:   FTP Server Denial of Service
Platforms:   Any
   Author:   Jose Miguel Esparza (jesparza () s21sec com)
      URL:   http://www.s21sec.com/avisos/s21sec-033-en.txt
  Release:   Public

[ SUMMARY ]

WzdFTPD is a ftp server designed to be modular and portable, work  
under linux/win32/freebsd/openbsd, and to be entirely configurable  
online using SITE commands. It supports SSL, IPv6, multithreading,  
external scripts, and it uses Unix-like permissions and ACLs, with  
virtual users and groups.

WzdFTPD project also supports bandwith limitation (per user, per  
group, or globally), group administrators, and per command  
authorization.


[ AFFECTED VERSIONS ]

Following versions are affected with this issue:

        - WzdFTPD v8.0 and prior.
        - Lastest version (8.1) is not affected by this vulnerability.


[ DESCRIPTION ]

It's possible to cause a denial of service sending a special crafted  
FTP command.


[ WORKAROUND ]

Add "key != NULL" condition in the chtbl_lookup function of the  
hash.c file until vendor solution or upgrade to 8.1.


[ ACKNOWLEDGMENTS ]

These vulnerabilities have been found and researched by:

        - Jose Miguel Esparza <jesparza () s21sec com> S21Sec

With thanks to:

        - David Barroso <dbarroso () s21sec com> S21Sec   


[ REFERENCES ]

* WzdFTPD
  http://www.wzdftpd.net/

* S21Sec
  http://www.s21sec.com