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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: [email protected]
         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.

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  Revision History
October 19, 1999:  Initial release

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