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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: certat_private
Phone: +1 412-268-7090 (24-hour hotline)
Fax: +1 412-268-6989
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Revision History
October 19, 1999: Initial release
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