__________________________________________________________
The U.S. Department of Energy
Computer Incident Advisory Center
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INFORMATION BULLETIN
FreeBSD tcpdump Remote Buffer Overflow Vulnerability
[FreeBSD Security Advisory 01:48]
July 23, 2001 22:00 GMT Number L-122
______________________________________________________________________________
PROBLEM: A remote buffer overflow exists in tcpdump.
PLATFORM: All releases of FreeBSD 4.x prior to 4.4
DAMAGE: Due to incorrect string length handling in the decoding of AFS
RPC packets, a remote user may be able to overflow a buffer
causing the local tcpdump process to crash. In addition, it may
be possible to execute arbitrary code with the privileges of the
user running tcpdump, that is often root.
SOLUTION: Upgrade your FreeBSD system to 4.3-STABLE or apply the
appropriate patch for your release as prescribed by FreeBSD.
______________________________________________________________________________
VULNERABILITY The risk is HIGH. The tcpdump runs as root, therefore having
ASSESSMENT: the potential to give an unauthorized person remote root
access.
______________________________________________________________________________
LINKS:
CIAC BULLETIN: http://www.ciac.org/ciac/bulletins/l-122.shtml
ORIGINAL BULLETIN:
ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-01%3A48.tcpdump.asc
______________________________________________________________________________
[***** Start FreeBSD Security Advisory 01:48 *****]
FreeBSD-SA-01:48 Security Advisory
FreeBSD, Inc.
Topic: tcpdump contains remote buffer overflow
Category: core
Module: tcpdump
Announced: 2001-07-17
Credits: Nick Cleaton <nick@cleaton.net>
Affects: All releases of FreeBSD 4.x prior to 4.4,
FreeBSD 4.3-STABLE prior to the correction date
FreeBSD 3.x is unaffected.
Corrected: 2001-07-09
Vendor status: Patch released
FreeBSD only: NO
I. Background
tcpdump is a tool for monitoring network traffic activity.
II. Problem Description
An overflowable buffer was found in the version of tcpdump included
with FreeBSD 4.x. Due to incorrect string length handling in the
decoding of AFS RPC packets, a remote user may be able to overflow a
buffer causing the local tcpdump process to crash. In addition, it
may be possible to execute arbitrary code with the privileges of the
user running tcpdump, often root.
The effects of this vulnerability are similiar to those described in
advisory FreeBSD-SA-00:61.tcpdump.v1.1.
All released versions of FreeBSD prior to the correction date
including 4.3-RELEASE are vulnerable to this problem, however it does
not affect the FreeBSD 3.x branch which includes an older version of
tcpdump.
III. Impact
Remote users can cause the local tcpdump process to crash, and may be
able to cause arbitrary code to be executed as the user running
tcpdump, often root.
IV. Workaround
Do not use vulnerable versions of tcpdump in network environments
which may contain packets from untrusted sources.
V. Solution
One of the following:
1) Upgrade your vulnerable FreeBSD system to 4.3-STABLE or the
RELENG_4_3 security branch after the respective correction dates.
2) FreeBSD 4.x systems prior to the correction date:
Download the patch and the detached PGP signature from the following
locations, and verify the signature using your PGP utility.
ftp://ftp.freebsd.org/pub/FreeBSD/CERT/patches/SA-01:48/tcpdump-4.x.patch
ftp://ftp.freebsd.org/pub/FreeBSD/CERT/patches/SA-01:48/tcpdump-4.x.patch.asc
# cd /usr/src/contrib/tcpdump
# patch -p < /path/to/patch
# cd /usr/src/usr.sbin/tcpdump
# make depend && make all install
3) FreeBSD 4.3-RELEASE systems:
An experimental upgrade package is available for users who wish to
provide testing and feedback on the binary upgrade process. This
package may be installed on FreeBSD 4.3-RELEASE systems only, and is
intended for use on systems for which source patching is not practical
or convenient.
If you use the upgrade package, feedback (positive or negative) is
requested to security-officer@FreeBSD.org so we can improve the
process for future advisories.
During the installation procedure, backup copies are made of the files
which are replaced by the package. These backup copies will be
reinstalled if the package is removed, reverting the system to a
pre-patched state.
Two versions of the upgrade package are available, depending on
whether or not the system has openssl installed. To verify whether
your system has openssl installed, perform the following command:
# ls /usr/bin/openssl
Possible responses:
/usr/bin/openssl # This response indicates you have openssl present
ls: /usr/bin/openssl: No such file or directory
# This reponse indicates you do not have
# openssl present
3a) If OpenSSL is not present
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/packages/SA-01:48/security-patch-tcpdump-nossl-01.48.tgz
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/packages/SA-01:48/security-patch-tcpdump-nossl-01.48.tgz.asc
Verify the detached PGP signature using your PGP utility.
# pkg_add security-patch-tcpdump-nossl-01.48.tgz
3b) If OpenSSL is present
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/packages/SA-01:48/security-patch-tcpdump-ssl-01.48.tgz
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/packages/SA-01:48/security-patch-tcpdump-ssl-01.48.tgz.asc
Verify the detached PGP signature using your PGP utility.
# pkg_add security-patch-tcpdump-ssl-01.48.tgz
[***** End FreeBSD Security Advisory 01:48 *****]
_______________________________________________________________________________
CIAC wishes to acknowledge the contributions of FreeBSD for the
information contained in this bulletin.
_______________________________________________________________________________
CIAC, the Computer Incident Advisory Center, is the computer
security incident response team for the U.S. Department of Energy
(DOE) and the emergency backup response team for the National
Institutes of Health (NIH). CIAC is located at the Lawrence Livermore
National Laboratory in Livermore, California. CIAC is also a founding
member of FIRST, the Forum of Incident Response and Security Teams, a
global organization established to foster cooperation and coordination
among computer security teams worldwide.
CIAC services are available to DOE, DOE contractors, and the NIH. CIAC
can be contacted at:
Voice: +1 925-422-8193 (7x24)
FAX: +1 925-423-8002
STU-III: +1 925-423-2604
E-mail: ciac@ciac.org
Previous CIAC notices, anti-virus software, and other information are
available from the CIAC Computer Security Archive.
World Wide Web: http://www.ciac.org/
Anonymous FTP: ftp.ciac.org
PLEASE NOTE: Many users outside of the DOE, ESnet, and NIH computing
communities receive CIAC bulletins. If you are not part of these
communities, please contact your agency's response team to report
incidents. Your agency's team will coordinate with CIAC. The Forum of
Incident Response and Security Teams (FIRST) is a world-wide
organization. A list of FIRST member organizations and their
constituencies can be obtained via WWW at http://www.first.org/.
This document was prepared as an account of work sponsored by an
agency of the United States Government. Neither the United States
Government nor the University of California nor any of their
employees, makes any warranty, express or implied, or assumes any
legal liability or responsibility for the accuracy, completeness, or
usefulness of any information, apparatus, product, or process
disclosed, or represents that its use would not infringe privately
owned rights. Reference herein to any specific commercial products,
process, or service by trade name, trademark, manufacturer, or
otherwise, does not necessarily constitute or imply its endorsement,
recommendation or favoring by the United States Government or the
University of California. The views and opinions of authors expressed
herein do not necessarily state or reflect those of the United States
Government or the University of California, and shall not be used for
advertising or product endorsement purposes.
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