Original release date: October 19, 1999<BR>
Last revised: November 9, 1999<BR>
Added vendor information for Fujitsu.<BR>
Source: CERT/CC<BR>

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

<H3>Systems Affected</H3>

<LI>Systems running the WU-FTPD daemon or its derivatives

<H2>I. Description</H2>

<P>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.

<H4>Vulnerability #1: MAPPING_CHDIR Buffer Overflow</H4>

<P>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.

<P>This is the same vulnerability described in AUSCERT Advisory
AA-1999.01, which is available from

  <A HREF="ftp://www.auscert.org.au/security/advisory/AA-1999.01.wu-ftpd.mapping_chdir.vul">ftp://www.auscert.org.au/security/advisory/AA-1999.01.wu-ftpd.mapping_chdir.vul</A>

<P>This is not the same vulnerability as the one described in
<A HREF="http://www.cert.org/advisories/CA-99-03-FTP-Buffer-Overflows.html">
CA-99-03 "FTP Buffer Overflows"</A>, 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.

<H4>Vulnerability #2: Message File Buffer Overflow</H4>

<P>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.

<P>This is one of the vulnerabilities described in AUSCERT Advisory
AA-1999.02, which is available from

  <A HREF="ftp://www.auscert.org.au/security/advisory/AA-1999.02.multi.wu-ftpd.vuls">ftp://www.auscert.org.au/security/advisory/AA-1999.02.multi.wu-ftpd.vuls</A>

<H4>Vulnerability #3: SITE NEWER Consumes Memory</H4>

<P>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.

<H2>II. Impact</H2>

<H4>Vulnerability #1: MAPPING_CHDIR Buffer Overflow</H4>

<P>Remote and local intruders may be able exploit this vulnerability
to execute arbitrary code as the user running the ftpd daemon, usually

<P>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.

<H4>Vulnerability #2: Message File Buffer Overflow</H4>

<P>Remote and local intruders may be able exploit this vulnerability
to execute arbitrary code as the user running the ftpd daemon, usually

<P>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

<P>Additionally, under some circumstances, remote intruders may be
able to take advantage of message files containing macros provided by
the FTP administrator.

<H4>Vulnerability #3: SITE NEWER Consumes Memory</H4>

<P>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.

<H2>III. Solution</H2>

<H4>Install appropriate patches from your vendor</H4>

<P>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.

<P>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.

<P>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.

<P>Until you can install a patch, you can apply the following

<H4>Vulnerability #1: MAPPING_CHDIR Buffer Overflow</H4>

<P>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.

<H4>Vulnerability #2: Message File Buffer Overflow</H4>

<P>Remote exploitation of this vulnerability can be mitigated and
possibly eliminated by removing macros from message files until a
patch can be applied.

<H4>Vulnerability #3: SITE NEWER Consumes Memory</H4>

<P>There are currently no workarounds available.

<H2><A NAME="vendor"></A>Appendix A. Vendor Information</H2>

<H4><U>Data General</U></H4>

<P>DG/UX is not vulnerable to this problem.


<P>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.


<P>The Fujitsu UXP/V Operating System is not vulnerable.

<H4><U>IBM Corporation</U></H4>

<P>AIX is not vulnerable.  It does not ship wu-ftpd.
<P>IBM and AIX are registered trademarks of International Business
Machines Corporation.


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

<H4><U>Santa Cruz Operation, Inc.</U></H4>

<P>Security patches for SCO UnixWare 7.x, SCO UnixWare 2.x, and
OpenServer 5.x will be made available at 
<A HREF="http://www.sco.com/security">http://www.sco.com/security</A>.


<P>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 
<A HREF="http://freeware.sgi.com/">http://freeware.sgi.com/</A>
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.

<P>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.

<P>SGI NT Workstations do not ship with wu-ftpd.


<P>Sun is not vulnerable.

<H4><U>WU-FTPD and BeroFTPD</U></H4>

<P>Vulnerability #1:

  <DD><P>Not vulnerable:<BR>
        versions 2.4.2 and all betas and earlier versions<BR>

        wu-ftpd-2.4.2-beta-18-vr4 through wu-ftpd-2.4.2-beta-18-vr15<BR>
        wu-ftpd-2.4.2-vr16 and wu-ftpd-2.4.2-vr17<BR>
        BeroFTPD, all versions

<P>Vulnerability #2:

  <DD><P>Not vulnerable:<BR>

        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.<BR>
        BeroFTPD, all versions<BR>

<P>Vulnerability #3:

  <DD><P>Not vulnerable:<BR>

        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.<BR>
        BeroFTPD, all versions<BR>

<P>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.

<P>WU-FTPD Version 2.6.0 is available for download from mirrors
arround the world.  A full list of mirrors is available from:

  <A HREF="ftp://ftp.wu-ftpd.org/pub/README-MIRRORS">

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

<DD><A HREF="ftp://ftp.wu-ftpd.org/pub/wu-ftpd/wu-ftpd-current.tar.gz">
<DD><A HREF="ftp://ftp.wu-ftpd.org/pub/wu-ftpd/wu-ftpd-current.tar.Z">


<P>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.

<p><!--#include virtual="/include/footer_nocopyright.html" --> </p>

<p>Copyright 1999 Carnegie Mellon University.</p>


Revision History
October 19, 1999  Initial release
November 9, 1999  Added vendor information for Fujitsu.