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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

   ftp://www.auscert.org.au/security/advisory/AA-1999.01.wu-ftpd.mapping_
          chdir.vul

   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

   ftp://www.auscert.org.au/security/advisory/AA-1999.02.multi.wu-ftpd.vu
          ls

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
   root.

   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
   root.

   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
   workarounds.

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

   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

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

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

   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
   fixes.

   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

   Sun is not vulnerable.

WU-FTPD and BeroFTPD

   Vulnerability #1:

   Not vulnerable:
          versions 2.4.2 and all betas and earlier versions
          Vulnerable:
          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
          wu-ftpd-2.5.0
          BeroFTPD, all versions

   Vulnerability #2:

   Not vulnerable:
          wu-ftpd-2.6.0
          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:
          wu-ftpd-2.6.0
          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:

   ftp://ftp.wu-ftpd.org/pub/README-MIRRORS

   The current version of WU-FTPD (presently 2.6.0) is also available
   from the primary distribution site:

   ftp://ftp.wu-ftpd.org/pub/wu-ftpd/wu-ftpd-current.tar.gz
          ftp://ftp.wu-ftpd.org/pub/wu-ftpd/wu-ftpd-current.tar.Z
     _________________________________________________________________

   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:
   http://www.cert.org/advisories/CA-99-13-wuftpd.html
   ______________________________________________________________________

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
          U.S.A.

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

   Revision History
October 19, 1999:  Initial release

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