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Category:   Application (E-mail Server)  >   Sendmail Vendors:   Sendmail Consortium
(FreeBSD Issues Fix) Sendmail DNS Map Initialization Flaw May Let Remote Users Crash the System
SecurityTracker Alert ID:  1007578
SecurityTracker URL:  http://securitytracker.com/id/1007578
CVE Reference:   CAN-2003-0688   (Links to External Site)
Date:  Aug 26 2003
Impact:   Denial of service via network, Execution of arbitrary code via network, User access via network
Fix Available:  Yes  Vendor Confirmed:  Yes  
Version(s): 8.12 - 8.12.8
Description:   A vulnerability was reported in certain versions of sendmail when using DNS maps in the sendmail configuration file. A remote user may be able to cause the mail service to crash or (in theory) execute arbitrary code.

Versions 8.12.x prior to version 8.12.9 are affected, but only when using DNS maps in the 'sendmail.cf' file.

It is reported that the dns_parse_reply() function improperly initializes RESOURCE_RECORD_T data structures. If sendmail receives a DNS reply where the reply size is not the reported size of the reply packet, the dns_free_data() function in the 'sm_resolve.c' file will attempt to free random memory addresses. This may cause sendmail to crash. The report indicates that this flaw may in theory allow a remote user to execute arbitrary code, but that is not confirmed in the report.

Oleg Bulyzhin is credited with reporting this flaw.
Impact:   A remote user may be able to return a DNS reply to sendmail that will cause the mail service to crash or [potentially/theoretically] execute arbitrary code.
Solution:   FreeBSD has released a fix and indicates that you should do one of the following:

1) Upgrade your vulnerable system to 4-STABLE, 5.1-RELEASE, or to the RELENG_5_1, RELENG_4_8, or RELENG_4_7 security branch dated after the correction date (5.1-RELEASE-p11, 4.8-RELEASE-p4, or 4.7-RELEASE-p14, respectively). See the Source Message for the correction dates.

2) Patch your present system:

The following patch has been verified to apply to FreeBSD 5.0, 4.8, 4.7, and 4.6 systems.

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

ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:11/sendmail.patch
ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:11/sendmail.patch.asc

b) Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch
# cd /usr/src/lib/libsm
# make obj && make depend && make
# cd /usr/src/lib/libsmutil
# make obj && make depend && make
# cd /usr/src/usr.sbin/sendmail
# make obj && make depend && make && make install

c) Restart sendmail. Execute the following command as root.

# /bin/sh /etc/rc.sendmail restart
Vendor URL:  www.sendmail.org/dnsmap1.html (Links to External Site)
Cause:   Resource error, State error
Underlying OS:   UNIX (FreeBSD)

Message History:   This archive entry is a follow-up to the message listed below.
Aug 25 2003 Sendmail DNS Map Initialization Flaw May Let Remote Users Crash the System


 Source Message Contents
Date:  Tue, 26 Aug 2003 09:43:31 -0700 (PDT)
Subject:  FreeBSD Security Advisory FreeBSD-SA-03:11.sendmail


-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

=============================================================================
FreeBSD-SA-03:11.sendmail                                   Security Advisory
                                                          The FreeBSD Project

Topic:          sendmail DNS map problem

Category:       contrib
Module:         contrib_sendmail
Announced:      2003-08-26
Credits:        Oleg Bulyzhin <oleg@rinet.ru>
Affects:        4.6-RELEASE (up to -p16), 4.7-RELEASE (up to -p13),
                4.8-RELEASE (up to -p3), 5.0-RELEASE (up to -p11)
                4-STABLE prior to Mar 29 19:33:18 2003 UTC
Corrected:      2003-08-25 22:33:14 UTC (RELENG_5_0)
                2003-08-25 22:35:23 UTC (RELENG_4_8)
                2003-08-25 22:36:10 UTC (RELENG_4_7)
                2003-08-25 22:38:53 UTC (RELENG_4_6)
FreeBSD only:   NO

For general information regarding FreeBSD Security Advisories,
including descriptions of the fields above, security branches, and the
following sections, please visit
<URL:http://www.freebsd.org/security/>.

I.   Background

FreeBSD includes sendmail(8), a general purpose internetwork mail
routing facility, as the default Mail Transfer Agent (MTA).

II.  Problem Description

Some versions of sendmail (8.12.0 through 8.12.8) contain a
programming error in the code that implements DNS maps.  A malformed
DNS reply packet may cause sendmail to call `free()' on an
uninitialized pointer.

NOTE: The default sendmail configuration in FreeBSD does not utilize
DNS maps.

III. Impact

Calling `free()' on an uninitialized pointer may result in a sendmail
child process crashing.  It may also be possible for an attacker to
somehow influence the value of the `uninitialized pointer' and cause
an arbitrary memory trunk to be freed.  This could further lead to
some other exploitable vulnerability, although no such cases are known
at this time.

IV.  Workaround

Do not use DNS maps.

V.   Solution

Do one of the following:

1) Upgrade your vulnerable system to 4-STABLE, 5.1-RELEASE, or to the
RELENG_5_1, RELENG_4_8, or RELENG_4_7 security branch dated after the
correction date (5.1-RELEASE-p11, 4.8-RELEASE-p4, or 4.7-RELEASE-p14,
respectively).

2) To patch your present system:

The following patch has been verified to apply to FreeBSD 5.0, 4.8,
4.7, and 4.6 systems.

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

ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:11/sendmail.patch
ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:11/sendmail.patch.asc

b) Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch
# cd /usr/src/lib/libsm
# make obj && make depend && make
# cd /usr/src/lib/libsmutil
# make obj && make depend && make
# cd /usr/src/usr.sbin/sendmail
# make obj && make depend && make && make install

c) Restart sendmail.  Execute the following command as root.

# /bin/sh /etc/rc.sendmail restart

VI.  Correction details

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

Path                                                             Revision
  Branch
- -------------------------------------------------------------------------
src/UPDATING
  RELENG_5_0                                                   1.229.2.17
  RELENG_4_8                                                1.73.2.80.2.6
  RELENG_4_7                                               1.73.2.74.2.17
  RELENG_4_6                                               1.73.2.68.2.45
src/sys/conf/newvers.sh
  RELENG_5_0                                                    1.48.2.12
  RELENG_4_8                                                1.44.2.29.2.5
  RELENG_4_7                                               1.44.2.26.2.16
  RELENG_4_6                                               1.44.2.23.2.34
src/contrib/sendmail/src/sm_resolve.c
  RELENG_5_0                                                  1.1.1.4.2.1
  RELENG_4_8                                              1.1.1.1.2.2.4.1
  RELENG_4_7                                              1.1.1.1.2.2.2.1
  RELENG_4_6                                              1.1.1.1.2.1.2.2
- -------------------------------------------------------------------------

VII. References

<URL:http://www.sendmail.org/dnsmap1.html>
<URL:http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2003-0688>
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.2.2 (FreeBSD)

iD8DBQE/S4xUFdaIBMps37IRAoJ4AJ9AiL4AMlSXz/thD2SuNkKSQsUZHgCeKbds
qEb9Em5ElZZOEnIajwneKIg=
=SjNG
-----END PGP SIGNATURE-----
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