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=============================================================================
FreeBSD-SA-02:29                                            Security Advisory
                                                          The FreeBSD Project

Topic:          Buffer overflow in tcpdump when handling NFS packets

Category:       contrib
Module:         tcpdump
Announced:      2002-07-12
Credits:        dwmw2@redhat.com
Affects:        All releases prior to and including 4.6-RELEASE
                FreeBSD 4.6-STABLE prior to the correction date
Corrected:      2002-07-05 13:24:57 UTC (RELENG_4)
                2002-07-12 13:29:47 UTC (RELENG_4_6)
                2002-07-12 13:31:10 UTC (RELENG_4_5)
                2002-07-12 13:31:44 UTC (RELENG_4_4)
FreeBSD only:   NO

I.   Background

The tcpdump utility is used to capture and examining network traffic.

II.  Problem Description

Versions of tcpdump up to and including 3.7.1 contain a buffer
overflow that may be triggered by badly formed NFS packets, and
possibly other types of packets.

III. Impact

It is not currently known whether this buffer overflow is exploitable.
If it were, an attacker could inject specially crafted packets into
the network which, when processed by tcpdump, could lead to arbitrary
code execution with the privileges of the user running tcpdump
(typically `root').

IV.  Workaround

There is no workaround, other than not using tcpdump.

V.   Solution

Do one of the following:

1) Upgrade your vulnerable system to 4.6-STABLE; or to the RELENG_4_6,
RELENG_4_5, or RELENG_4_4 security branch dated after the correction
date (4.6-RELEASE-p2, 4.5-RELEASE-p8, or 4.4-RELEASE-p15).

2) To patch your present system:

The following patch has been verified to apply to FreeBSD 4.4, 4.5, and
4.6 systems.

a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.

# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-02:29/tcpdump.patch
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-02:29/tcpdump.patch.asc

b) Execute the following commands as root:

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

VI.  Correction details

The following list contains the revision numbers of each file that was
corrected in FreeBSD.

Path                                                             Revision
  Branch
- -------------------------------------------------------------------------
src/contrib/tcpdump/interface.h
  RELENG_4                                                        1.4.2.3
  RELENG_4_6                                                  1.4.2.1.6.1
  RELENG_4_5                                                  1.4.2.1.4.1
  RELENG_4_4                                                  1.4.2.1.2.1
- -------------------------------------------------------------------------

VII. References

<URL:http://rhn.redhat.com/errata/RHSA-2002-094.html>
<URL:http://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=55145>
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