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Tcpdump Remote Buffer Overflows

Tcpdump Remote Buffer Overflows Privacy and Legal Notice CIAC INFORMATION BULLETIN L-015: Tcpdump Remote Buffer Overflows October 31, 2000 13:00 GMT

PROBLEM:       Tcpdump version 3.5 contains remote buffer overflows that
               results in tcpdump crashing or allowing the remote attacker to
               execute arbitrary code as root.
PLATFORM:      Linux and BSD operating systems
DAMAGE:        A remote user will be able to gain root or crash some Intrusion
               Detection systems.
SOLUTION:      Upgrade to the latest version of tcpdump, 3.5.2.
VULNERABILITY  The risk is HIGH.  Expolit code is not publically available,
ASSESSMENT:    but the application is common to many default OS installs.


Background

Tcpdump is a free sniffer developed first by Lawrence Berkeley National
Laboratory, and now is maintained by a consortium.  It is most commonly used
to capture ethernet packets in a common format that many analysis tools can
read.  It is the basis for many Intrusion Detection Software applications.

It is now bundled with many linux and BSD type operating systems and is
sometimes installed with the default installation package.

Issue

During internal source code auditing done by FreeBSD, several overflowable
buffers were discovered in the version of tcpdump included in many OS'.  Some
simply allow the remote attacker to crash the local tcpdump process.  This
is a problem for systems using tcpdump as a form of intrusion detection, as
after an attacker has crashed the tcpdump process, network activity will no
longer occur.

There is a more serious vulnerability in the decoding of AFS ACL packets in
the more recent version of tcpdump (tcpdump 3.5) which may allow a remote
attacker to execute arbitrary code on the local system (usually at root
privilege, since root privilege is required to run tcpdump).

Fix

Do not use vulnerable versions of tcpdump.  Upgrade to the most recent version
of the application (3.5.2) from www.tcpdump.org, or consult you OS vendor for
a fix.  For example, for FreeBSD:

a) FreeBSD 3.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-00:61/tcpdump-3.x.patch
ftp://ftp.freebsd.org/pub/FreeBSD/CERT/patches/SA-00:61/tcpdump-3.x.patch.asc

# cd /usr/src/contrib/tcpdump
# patch -p < /path/to/patch
# cd /usr/src/usr.sbin/tcpdump
# make depend && make all install

b) 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-00:61/tcpdump-4.x.patch
ftp://ftp.freebsd.org/pub/FreeBSD/CERT/patches/SA-00:61/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

CIAC wishes to acknowledge the contributions of FreeBSD for information contained in this bulletin.

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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.

UCRL-MI-119788
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