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Home : Advisories : Multiple Vulnerabilities in WU-FTPD

Title: Multiple Vulnerabilities in WU-FTPD
Released by: CERT
Date: 19th October 1999
Printable version: Click here

Hash: SHA1

CERT Advisory CA-99-13 Multiple Vulnerabilities in WU-FTPD

   Original release date: October 19, 1999

   Last revised: --

   Source: CERT/CC


   A complete revision history is at the end of this file.


Systems Affected

     * Systems running the WU-FTPD daemon or its derivatives


I. Description

   Three vulnerabilities have been identified in WU-FTPD and other ftp

   daemons based on the WU-FTPD source code. WU-FTPD is a common package

   used to provide File Transfer Protocol (FTP) services. Incidents

   involving at least the first of these vulnerabilities have been

   reported to the CERT Coordination Center.


Vulnerability #1: MAPPING_CHDIR Buffer Overflow

   Because of improper bounds checking, it is possible for an intruder to

   overwrite static memory in certain configurations of the WU-FTPD

   daemon. The overflow occurs in the MAPPING_CHDIR portion of the source

   code and is caused by creating directories with carefully chosen

   names. As a result, FTP daemons compiled without the MAPPING_CHDIR

   option are not vulnerable.


   This is the same vulnerability described in AUSCERT Advisory

   AA-1999.01, which is available from





   This is not the same vulnerability as the one described in CA-99-03

   "FTP Buffer Overflows", even though it is closely related. Systems

   that have patches to correct the issue described in CA-99-03 may still

   be vulnerable to this problem.


Vulnerability #2: Message File Buffer Overflow

   Because of improper bounds checking during the expansion of macro

   variables in the message file, intruders may be able to overwrite the

   stack of the FTP daemon.


   This is one of the vulnerabilities described in AUSCERT Advisory

   AA-1999.02, which is available from





Vulnerability #3: SITE NEWER Consumes Memory

   The SITE NEWER command is a feature specific to WUFTPD designed to

   allow mirroring software to identify all files newer than a supplied

   date. This command fails to free memory under some circumstances.


II. Impact

Vulnerability #1: MAPPING_CHDIR Buffer Overflow

   Remote and local intruders may be able exploit this vulnerability to

   execute arbitrary code as the user running the ftpd daemon, usually



   To exploit this vulnerability, the intruder must be able to create

   directories on the vulnerable systems that are accessible via FTP.

   While remote intruders are likely to have this privilege only through

   anonymous FTP access, local users may be able to create the required

   directories in their own home directories.


Vulnerability #2: Message File Buffer Overflow

   Remote and local intruders may be able exploit this vulnerability to

   execute arbitrary code as the user running the ftpd daemon, usually



   If intruders are able to control the contents of a message file, they

   can successfully exploit this vulnerability. This access is frequently

   available to local users in their home directories, but it may be

   restricted in anonymous FTP access, depending on your configuration.


   Additionally, under some circumstances, remote intruders may be able

   to take advantage of message files containing macros provided by the

   FTP administrator.


Vulnerability #3: SITE NEWER Consumes Memory

   Remote and local intruders who can connect to the FTP server can cause

   the server to consume excessive amounts of memory, preventing normal

   system operation. If intruders can create files on the system, they

   may be able exploit this vulnerability to execute arbitrary code as

   the user running the ftpd daemon, usually root.


III. Solution

Install appropriate patches from your vendor

   These vulnerabilities can be eliminated by applying appropriate

   patches from your vendor. We encourage you to apply a patch as soon as

   possible and to disable vulnerable programs until you can do so.


   Disabling the WU-FTPD daemon may prevent your system from operating

   normally. Upgrading to WU-FTPD 2.6.0 may cause some inter-operability

   problems with certain FTP clients. We encourage you to review the

   WU-FTPD documentation carefully before performing this upgrade.


   Appendix A contains information provided by vendors for this advisory.

   We will update the appendix as we receive more information. If you do

   not see your vendor's name, the CERT/CC did not hear from that vendor.

   Please contact your vendor directly.


   Until you can install a patch, you can apply the following



Vulnerability #1: MAPPING_CHDIR Buffer Overflow

   This vulnerability can be corrected by compiling the WU-FTPD daemon

   without the MAPPING_CHDIR option. Exploitation by anonymous remote

   intruders can be mitigated by limiting write access, but this solution

   is not encouraged.


Vulnerability #2: Message File Buffer Overflow

   Remote exploitation of this vulnerability can be mitigated and

   possibly eliminated by removing macros from message files until a

   patch can be applied.


Vulnerability #3: SITE NEWER Consumes Memory

   There are currently no workarounds available.


Appendix A. Vendor Information

Data General

   DG/UX is not vulnerable to this problem.



   FreeBSD has updated its wuftpd and proftpd ports to correct this

   problem as of August 30, 1999. Users of these ports are encouraged to

   upgrade their installation to these newer versions of these ports as

   soon as possible.


IBM Corporation

   AIX is not vulnerable. It does not ship wu-ftpd.


   IBM and AIX are registered trademarks of International Business

   Machines Corporation.



   OpenBSD does not use (and never will use) wuftpd or any of its



Santa Cruz Operation, Inc.

   Security patches for SCO UnixWare 7.x, SCO UnixWare 2.x, and

   OpenServer 5.x will be made available at http://www.sco.com/security.



   SGI IRIX and Unicos do not ship with wu-ftpd, so they are not

   vulnerable. As a courtesy, unsupported pre-compiled IRIX inst images

   for wu-ftpd are available from http://freeware.sgi.com/ which may be

   vulnerable. When the freeware products are next updated, they should

   contain the latest wu-ftpd code which should include the security



   SGI Linux 1.0 which is based on RedHat 6.0 ships with wu-ftpd rpms.

   When new wu-ftpd rpms are available for RedHat 6.0, they can be

   installed on SGI Linux 1.0.


   SGI NT Workstations do not ship with wu-ftpd.



   Sun is not vulnerable.



   Vulnerability #1:


   Not vulnerable:

          versions 2.4.2 and all betas and earlier versions


          wu-ftpd-2.4.2-beta-18-vr4 through wu-ftpd-2.4.2-beta-18-vr15

          wu-ftpd-2.4.2-vr16 and wu-ftpd-2.4.2-vr17


          BeroFTPD, all versions


   Vulnerability #2:


   Not vulnerable:



          All versions of wuarchive-ftpd and wu-ftpd prior to version

          2.6.0, from wustl.edu, academ.com, vr.net and wu-ftpd.org.

          BeroFTPD, all versions


   Vulnerability #3:


   Not vulnerable:



          All versions of wuarchive-ftpd and wu-ftpd prior to version

          2.6.0, from wustl.edu, academ.com, vr.net and wu-ftpd.org.

          BeroFTPD, all versions


   With version 2.6.0, the major functionality of BeroFTPD has been

   merged back into the WU-FTPD daemon. Development of BeroFTPD has

   ceased; there will be no upgrades or patches. Users are advised to

   upgrade to WU-FTPD version 2.6.0.


   WU-FTPD Version 2.6.0 is available for download from mirrors arround

   the world. A full list of mirrors is available from:




   The current version of WU-FTPD (presently 2.6.0) is also available

   from the primary distribution site:






   The CERT Coordination Center would like to thank Gregory Lundberg (a

   member of the WU-FTPD development group) and AUSCERT their assistance

   in preparing this advisory.



   This document is available from:




CERT/CC Contact Information

   Email: cert@cert.org

          Phone: +1 412-268-7090 (24-hour hotline)

          Fax: +1 412-268-6989

          Postal address:

          CERT Coordination Center

          Software Engineering Institute

          Carnegie Mellon University

          Pittsburgh PA 15213-3890



   CERT personnel answer the hotline 08:00-20:00 EST(GMT-5) / EDT(GMT-4)

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   Copyright 1999 Carnegie Mellon University.

   Conditions for use, disclaimers, and sponsorship information can be

   found in




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   Any material furnished by Carnegie Mellon University and the Software

   Engineering Institute is furnished on an "as is" basis. Carnegie

   Mellon University makes no warranties of any kind, either expressed or

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   Revision History

October 19, 1999:  Initial release


Version: PGP for Personal Privacy 5.0

Charset: noconv





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