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CA-2003-07 Remote Buffer Overflow in Sendmail

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CERT Advisory CA-2003-07 Remote Buffer Overflow in Sendmail

Original release date: March 3, 2003
Last revised: --
Source: CERT/CC

A complete revision history can be found at the end of this file.

Systems Affected

* Sendmail Pro (all versions)
* Sendmail Switch 2.1 prior to 2.1.5
* Sendmail Switch 2.2 prior to 2.2.5
* Sendmail Switch 3.0 prior to 3.0.3
* Sendmail for NT 2.X prior to 2.6.2
* Sendmail for NT 3.0 prior to 3.0.3
* Systems running open-source sendmail versions prior to 8.12.8,
including UNIX and Linux systems

Overview

There is a vulnerability in sendmail that may allow remote attackers
to gain the privileges of the sendmail daemon, typically root.

I. Description

Researchers at Internet Security Systems (ISS) have discovered a
remotely exploitable vulnerability in sendmail. This vulnerability
could allow an intruder to gain control of a vulnerable sendmail
server.

Most organizations have a variety of mail transfer agents (MTAs) at
various locations within their network, with at least one exposed to
the Internet. Since sendmail is the most popular MTA, most
medium-sized to large organizations are likely to have at least one
vulnerable sendmail server. In addition, many UNIX and Linux
workstations provide a sendmail implementation that is enabled and
running by default.

This vulnerability is message-oriented as opposed to
connection-oriented. That means that the vulnerability is triggered by
the contents of a specially-crafted email message rather than by
lower-level network traffic. This is important because an MTA that
does not contain the vulnerability will pass the malicious message
along to other MTAs that may be protected at the network level. In
other words, vulnerable sendmail servers on the interior of a network
are still at risk, even if the site's border MTA uses software other
than sendmail. Also, messages capable of exploiting this vulnerability
may pass undetected through many common packet filters or firewalls.

Sendmail has indicated to the CERT/CC that this vulnerability has been
successfully exploited in a laboratory environment. We do not believe
that this exploit is available to the public. However, this
vulnerability is likely to draw significant attention from the
intruder community, so the probability of a public exploit is high.

A successful attack against an unpatched sendmail system will not
leave any messages in the system log. However, on a patched system, an
attempt to exploit this vulnerability will leave the following log
message:

Dropped invalid comments from header address

Although this does not represent conclusive evidence of an attack, it
may be useful as an indicator.

A patched sendmail server will drop invalid headers, thus preventing
downstream servers from receiving them.

The CERT/CC is tracking this issue as VU#398025. This reference number
corresponds to CVE candidate CAN-2002-1337.

For more information, please see

http://www.sendmail.org
http://www.sendmail.org/8.12.8.html
http://www.sendmail.com/security/
http://www.iss.net/issEn/delivery/xforce/alertdetail.jsp?oid=21950
http://www.kb.cert.org/vuls/id/398025

II. Impact

Successful exploitation of this vulnerability may allow an attacker to
gain the privileges of the sendmail daemon, typically root. Even
vulnerable sendmail servers on the interior of a given network may be
at risk since the vulnerability is triggered from the contents of a
malicious email message.

III. Solution

Apply a patch from Sendmail

Sendmail has produced patches for versions 8.9, 8.10, 8.11, and 8.12.
However, the vulnerability also exists in earlier versions of the
code; therefore, site administrators using an earlier version are
encouraged to upgrade to 8.12.8. These patches are located at

ftp://ftp.sendmail.org/pub/sendmail/sendmail.8.12.security.cr.patch
ftp://ftp.sendmail.org/pub/sendmail/sendmail.8.11.6.security.cr.patch
ftp://ftp.sendmail.org/pub/sendmail/sendmail.8.9.3.security.cr.patch

Apply a patch from your vendor

Many vendors include vulnerable sendmail servers as part of their
software distributions. We have notified vendors of this vulnerability
and recorded their responses in the systems affected section of
VU#398025. Several vendors have provided a statement for direct
inclusion in this advisory; these statements are available in Appendix
A.

Enable the RunAsUser option

There is no known workaround for this vulnerability. Until a patch can
be applied, you may wish to set the RunAsUser option to reduce the
impact of this vulnerability. As a good general practice, the CERT/CC
recommends limiting the privileges of an application or service
whenever possible.

Appendix A. - Vendor Information

This appendix contains information provided by vendors for this
advisory. As vendors report new information to the CERT/CC, we will
update this section and note the changes in our revision history. If a
particular vendor is not listed below, we have not received their
comments.

Apple Computer, Inc.

Security Update 2003-03-03 is available to fix this issue. Packages
are available for Mac OS X 10.1.5 and Mac OS X 10.2.4. It should be
noted that sendmail is not enabled by default on Mac OS X, so only
those systems which have explicitly enabled it are susceptible to the
vulnerability. All customers of Mac OS X, however, are encouraged to
apply this update to their systems.

Avaya, Inc.

Avaya is aware of the vulnerability and is investigating impact. As
new information is available this statement will be updated.

BSD/OS

Wind River Systems has created patches for this problem which are
available from the normal locations for each release. The relevant
patches are M500-006 for BSD/OS version 5.0 or the Wind River Platform
for Server Appliances 1.0, M431-002 for BSD/OS 4.3.1, or M420-032 for
BSD/OS 4.2 systems.

Cisco Systems

Cisco is investigating this issue. If we determine any of our products
are vulnerable that information will be available at:
http://www.cisco.com/go/psirt

Cray Inc.

The code supplied by Cray, Inc. in Unicos, Unicos/mk, and Unicos/mp
may be vulnerable. Cray has opened SPRs 724749 and 724750 to
investigate.

Cray, Inc. is not vulnerable for the MTA systems.

Hewlett-Packard Company

SOURCE:
Hewlett-Packard Company
HP Services
Software Security Response Team

x-ref: SSRT3469 sendmail

HP will provide notice of the availability of patches through standard
security bulletin announcements and be available from your normal HP
Services support channel.

IBM Corporation

The AIX operating system is vulnerable to the sendmail issues
discussed in releases 4.3.3, 5.1.0 and 5.2.0.

A temporary patch is available through an efix package which can be
found at
ftp://ftp.software.ibm.com/aix/efixes/security/sendmail_efix.tar.Z

IBM will provide the following official fixes:

APAR number for AIX 4.3.3: IY40500 (available approx.
03/12/2003)
APAR number for AIX 5.1.0: IY40501 (available approx.
04/28/2003)
APAR number for AIX 5.2.0: IY40502 (available approx.
04/28/2003)

Openwall GNU/*/Linux

Openwall GNU/*/Linux is not vulnerable. We use Postfix as the MTA, not
sendmail.

Red Hat Inc.

Updated sendmail packages that are not vulnerable to this issue are
available for Red Hat Linux, Red Hat Advanced Server, and Red Hat
Advanced Workstation. Red Hat Network users can update their systems
using the 'up2date' tool.

Red Hat Linux:

http://rhn.redhat.com/errata/RHSA-2003-073.html

Red Hat Linux Advanced Server, Advanced Workstation:

http://rhn.redhat.com/errata/RHSA-2003-074.html

SGI

SGI acknowledges VU#398025 reported by CERT and has released an
advisory to address the vulnerability on IRIX.

Refer to SGI Security Advisory 20030301-01-P available from
ftp://patches.sgi.com/support/free/security/advisories/20030301-01-P
or http://www.sgi.com/support/security/.

The Sendmail Consortium

The Sendmail Consortium suggests that sites upgrade to 8.12.8 if
possible. Alternatively, patches are available for 8.9, 8.10, 8.11,
and 8.12 on http://www.sendmail.org/

Sendmail, Inc.

All commercial releases including Sendmail Switch, Sendmail Advanced
Message Server (which includes the Sendmail Switch MTA), Sendmail for
NT, and Sendmail Pro are affected by this issue. Patch information is
available at http://www.sendmail.com/security.
_________________________________________________________________

Our thanks to Internet Security Systems, Inc. for discovering this
problem, and to Eric Allman, Claus Assmann, and Greg Shapiro of
Sendmail for notifying us of this problem. We thank both groups for
their assistance in coordinating the response to this problem.
_________________________________________________________________

Authors: Jeffrey P. Lanza and Shawn V. Hernan
______________________________________________________________________

This document is available from:
http://www.cert.org/advisories/CA-2003-07.html
______________________________________________________________________

CERT/CC Contact Information

Email: cert@cert.org
Phone: +1 412-268-7090 (24-hour hotline)
Fax: +1 412-268-6989
Postal address:
CERT Coordination Center
Software Engineering Institute
Carnegie Mellon University
Pittsburgh PA 15213-3890
U.S.A.

CERT/CC personnel answer the hotline 08:00-17:00 EST(GMT-5) /
EDT(GMT-4) Monday through Friday; they are on call for emergencies
during other hours, on U.S. holidays, and on weekends.

Using encryption

We strongly urge you to encrypt sensitive information sent by email.
Our public PGP key is available from
http://www.cert.org/CERT_PGP.key

If you prefer to use DES, please call the CERT hotline for more
information.

Getting security information

CERT publications and other security information are available from
our web site
http://www.cert.org/

To subscribe to the CERT mailing list for advisories and bulletins,
send email to majordomo@cert.org. Please include in the body of your
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* "CERT" and "CERT Coordination Center" are registered in the U.S.
Patent and Trademark Office.
______________________________________________________________________

NO WARRANTY
Any material furnished by Carnegie Mellon University and the Software
Engineering Institute is furnished on an "as is" basis. Carnegie
Mellon University makes no warranties of any kind, either expressed or
implied as to any matter including, but not limited to, warranty of
fitness for a particular purpose or merchantability, exclusivity or
results obtained from use of the material. Carnegie Mellon University
does not make any warranty of any kind with respect to freedom from
patent, trademark, or copyright infringement.
_________________________________________________________________

Conditions for use, disclaimers, and sponsorship information

Copyright 2003 Carnegie Mellon University.

Revision History
Mar 03, 2003: Initial release

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