Sendmail patch

Added patch to Sendmail 8.11.6 to fix buffer overflow problem reported on March 29, 2003 per CERT Advisory CA-2003-12 Buffer Overflow in Sendmail


CERT Advisory CA-2003-12 Buffer Overflow in Sendmail

Original release date: March 29, 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 2.1.6
* Sendmail Switch 2.2 prior to 2.2.6
* Sendmail Switch 3.0 prior to 3.0.4
* Sendmail for NT 2.X prior to 2.6.3
* Sendmail for NT 3.0 prior to 3.0.4
* Systems running open-source sendmail versions prior to 8.12.9,
including UNIX and Linux systems


There is a vulnerability in sendmail that can be exploited to cause a
denial-of-service condition and could allow a remote attacker to
execute arbitrary code with the privileges of the sendmail daemon,
typically root.

I. Description

There is a remotely exploitable vulnerability in sendmail that could
allow an attacker to gain control of a vulnerable sendmail server.
Address parsing code in sendmail does not adequately check the length
of email addresses. An email message with a specially crafted address
could trigger a stack overflow. This vulnerability was discovered by
Michal Zalewski.

This vulnerability is different than the one described in CA-2003-07.

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.

This vulnerability has been successfully exploited to cause a
denial-of-service condition in a laboratory environment. It is
possible that this vulnerability could be used to execute code on some
vulnerable systems.

The CERT/CC is tracking this issue as VU#897604. This reference number
corresponds to CVE candidate CAN-2003-0161.

For more information, please see

For the latest information about this vulnerability, including the
most recent vendor information, please see

This vulnerability is distinct from VU#398025.

II. Impact

Successful exploitation of this vulnerability may cause a
denial-of-service condition or 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 by the contents of a malicious
email message.

III. Solution

Apply a patch from Sendmail, Inc.

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 8.12.9. These patches, and a signature file,
are located at

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 the statements they provided in Appendix A of this
advisory. The most recent vendor information can be found in the
systems affected section of VU#897604.

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

Red Hat Inc.

Red Hat distributes sendmail in all Red Hat Linux distributions. We
are currently [Mar29] working on producing errata packages to correct
this issue, when complete these will be available along with our
advisory at the URL below. At the same time users of the Red Hat
Network will be able to update their systems using the ‘up2date’ tool.

Red Hat Linux:

Red Hat Enterprise Linux:

The Sendmail Consortium

The Sendmail Consortium recommends that sites upgrade to 8.12.9
whenever possible. Alternatively, patches are available for 8.9, 8.10,
8.11, and 8.12 on

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

Our thanks to Eric Allman, Claus Assmann, Greg Shapiro, and Dave
Anderson of Sendmail for reporting this problem and for their
assistance in coordinating the response to this problem. We also thank
Michal Zalewski for discovering this vulnerability.

Authors: Art Manion and Shawn V. Hernan

This document is available from:

CERT/CC Contact Information

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

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

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

Getting security information

CERT publications and other security information are available from
our web site

To subscribe to the CERT mailing list for advisories and bulletins,
send email to Please include in the body of your

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* “CERT” and “CERT Coordination Center” are registered in the U.S.
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Conditions for use, disclaimers, and sponsorship information

Copyright 2003 Carnegie Mellon University.
Revision History

March 29,2003: Initial release

Version: PGP 6.5.8