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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
Overview
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
http://www.sendmail.org
http://www.sendmail.org/8.12.9.html
http://www.sendmail.com/security/
For the latest information about this vulnerability, including the
most recent vendor information, please see
http://www.kb.cert.org/vuls/id/897604
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
ftp://ftp.sendmail.org/pub/sendmail/prescan.tar.gz.uu
ftp://ftp.sendmail.org/pub/sendmail/prescan.tar.gz.uu.asc
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
comments.
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:
http://rhn.redhat.com/errata/RHSA-2003-120.html
Red Hat Enterprise Linux:
http://rhn.redhat.com/errata/RHSA-2003-121.html
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 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 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:
http://www.cert.org/advisories/CA-2003-12.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
message
subscribe cert-advisory
* "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
March 29,2003: Initial release
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