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TUCoPS :: Unix :: General :: n-067.txt

Sendmail MTA Buffer Overflow Vulnerability (CIAC N-067)





             __________________________________________________________

                       The U.S. Department of Energy
                   Computer Incident Advisory Capability
                           ___  __ __    _     ___
                          /       |     /_\   /
                          \___  __|__  /   \  \___
             __________________________________________________________

                             INFORMATION BULLETIN

                   Sendmail MTA Buffer Overflow Vulnerability
                          [CERTŪ Advisory CA-2003-12]

March 31, 2003 15:00 GMT                                          Number N-067
[REVISED 18 Sept 2003]
______________________________________________________________________________
PROBLEM:       A remotely exploitable vulnerability has been identified
               where 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.
PLATFORM:      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
               IRIX 6.5.22 or patch 5287
DAMAGE:        Successful exploitation of this vulnerability may cause a
               denial-of-service condition or could 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.
SOLUTION:      Apply appropriate patches available from Sendmail, Inc., or
               from your respective vendor. 
               Alternative: upgrade to Sendmail version 8.12.9.
			   Monitor CERT's Advisory for vendor information updates.
______________________________________________________________________________
VULNERABILITY  The risk is HIGH. This vulnerability is message-oriented as
ASSESSMENT:    opposed to connection-oriented.  Connection-oriented defenses
               such as packet filters and firewalls might not detect the
               malicious e-mail.  In particular, a non-sendmail mail transfer
               agent (MTA) might pass on the malicious e-mail unchanged to
               vulnerable MTAs.
______________________________________________________________________________
LINKS:
 CIAC BULLETIN:      http://www.ciac.org/ciac/bulletins/n-067.shtml
 ORIGINAL BULLETIN:  http://www.cert.org/advisories/CA-2003-12.html
 PATCHES:            http://www.sendmail.com/security/
                     http://www.sendmail.org
                     http://www.sendmail.org/8.12.9.html
 ADDITIONAL LINK:    ftp://patches.sgi.com/support/free/security/advisories/
                     20030803-01-P
______________________________________________________________________________
REVISION HISTORY: 09/18/03 - Added SGI Security Advisory's patch link and IRIX 
                             to the Software section.


[***** Start CERTŪ Advisory CA-2003-12 *****]

CERTŪ Advisory CA-2003-12 Buffer Overflow in Sendmail

Original release date: March 29, 2003
Last revised: March 30, 2003
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. 

Conectiva

Conectiva Linux 6.0, 7.0 and 8 contain sendmail and are vulnerable to this 
issue, even though sendmail is no longer the default MTA in our distribution. 
Updated packages will be announced to our mailing lists when ready. 

Hewlett-Packard

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

x-ref: SSRT3531

At the time of writing this document, Hewlett Packard is currently 
investigating the potential impact to HP's released Operating System 
software products.

As further information becomes available HP will provide notice of 
the availability of any necessary patches through standard security 
bulletin announcements and be available from your normal HP Services 
support channel. 

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/. 

Wind River Systems Inc.

This vulnerability is addressed by the M500-008 patch for Platform for Server
Appliances 1.0 or BSD/OS 5.0 based systems. The M31--005 patch addresses this 
problem for BSD/OS 4.3.1 or 4.3 systems, and the M420-034 addresses this problem 
for BSD/OS 4.2 based systems. 



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
March 29, 2003: Added Conectiva statement, reformated vendor statements
March 30, 2003: Added Wind River Systems and HP statements 

[***** End CERTŪ Advisory CA-2003-12 *****]
_______________________________________________________________________________

CIAC wishes to acknowledge the contributions of CERT and Sendmail, Inc. for the
information contained in this bulletin.
_______________________________________________________________________________

CIAC, the Computer Incident Advisory Capability, is the computer
security incident response team for the U.S. Department of Energy
(DOE) and the emergency backup response team for the National
Institutes of Health (NIH). CIAC is located at the Lawrence Livermore
National Laboratory in Livermore, California. CIAC is also a founding
member of FIRST, the Forum of Incident Response and Security Teams, a
global organization established to foster cooperation and coordination
among computer security teams worldwide.

CIAC services are available to DOE, DOE contractors, and the NIH. CIAC
can be contacted at:
    Voice:    +1 925-422-8193 (7x24)
    FAX:      +1 925-423-8002
    STU-III:  +1 925-423-2604
    E-mail:   ciac@ciac.org

Previous CIAC notices, anti-virus software, and other information are
available from the CIAC Computer Security Archive.

   World Wide Web:      http://www.ciac.org/
   Anonymous FTP:       ftp.ciac.org

PLEASE NOTE: Many users outside of the DOE, ESnet, and NIH computing
communities receive CIAC bulletins.  If you are not part of these
communities, please contact your agency's response team to report
incidents. Your agency's team will coordinate with CIAC. The Forum of
Incident Response and Security Teams (FIRST) is a world-wide
organization. A list of FIRST member organizations and their
constituencies can be obtained via WWW at http://www.first.org/.

This document was prepared as an account of work sponsored by an
agency of the United States Government. Neither the United States
Government nor the University of California nor any of their
employees, makes any warranty, express or implied, or assumes any
legal liability or responsibility for the accuracy, completeness, or
usefulness of any information, apparatus, product, or process
disclosed, or represents that its use would not infringe privately
owned rights. Reference herein to any specific commercial products,
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otherwise, does not necessarily constitute or imply its endorsement,
recommendation or favoring by the United States Government or the
University of California. The views and opinions of authors expressed
herein do not necessarily state or reflect those of the United States
Government or the University of California, and shall not be used for
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