From: CERT Advisory (cert-advisorycert.org)
Date: Thu Sep 18 2003 - 09:38:29 CDT

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CERT Advisory CA-2003-25 Buffer Overflow in Sendmail

   Original issue date: September 18, 2003
   Last revised: --
   Source: CERT/CC

   A complete revision history is at the end of this file.

Systems Affected

     * Systems running open-source sendmail versions prior to 8.12.10,
       including UNIX and Linux systems

     * Commercial releases of sendmail including Sendmail Switch,
       Sendmail Advanced Message Server (SAMS), and Sendmail for NT

Overview

   A vulnerability in sendmail could allow a remote attacker to execute
   arbitrary code with the privileges of the sendmail daemon, typically
   root.

I. Description

   Sendmail is a widely deployed mail transfer agent (MTA). Many UNIX and
   Linux systems provide a sendmail implementation that is enabled and
   running by default. Sendmail contains a vulnerability in its address
   parsing code. An error in the prescan() function could allow an
   attacker to write past the end of a buffer, corrupting memory
   structures. Depending on platform and operating system architecture,
   the attacker may be able to execute arbitrary code with a specially
   crafted email message.

   This vulnerability is different than the one described in CA-2003-12.

   The email attack vector is message-oriented as opposed to
   connection-oriented. This 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 may 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 packet filters or firewalls.

   Further information is available in VU#784980. Common Vulnerabilities
   and Exposures (CVE) refers to this issue as CAN-2003-0694.

II. Impact

   Depending on platform and operating system architecture, a remote
   attacker could execute arbitrary code with the privileges of the
   sendmail daemon. Unless the RunAsUser option is set, Sendmail
   typically runs as root.

III. Solution

Upgrade or apply a patch

   This vulnerability is resolved in Sendmail 8.12.10. Sendmail has also
   released a patch that can be applied to Sendmail 8.9.x through 8.12.9.
   Information about specific vendors is available in Appendix A. and in
   the Systems Affected section of VU#784980.

   Sendmail 8.12.10 is designed to correct malformed messages that are
   transferred by the server. This should help protect other vulnerable
   sendmail servers.

Enable the RunAsUser option

   While there is no known complete workaround, consider setting the
   RunAsUser option to reduce the impact of this vulnerability. It is
   typically considered to be a good security practice to limit the
   privileges of applications and services whenever possible.

Appendix A. Vendor Information

   This appendix contains information provided by vendors. When vendors
   report new information, this section is updated, and the changes are
   noted in the revision history. If a vendor is not listed below, we
   have not received their direct statement. Further vendor information
   is available in the Systems Affected section of VU#784980.

Debian

     The sendmail and sendmail-wide packages are vulnerable to this
     issue. Updated packages are being prepared and will be available
     soon.

F5 Networks

     BIG-IP and 3-DNS products are not vulnerable.

IBM

     The AIX Security Team is aware of the issues discussed in CERT
     Vulnerability Note VU#784980.

     The following APARs will be released to address this issue:

      APAR number for AIX 4.3.3: IY48659 (available approx. 10/03/03)
      APAR number for AIX 5.1.0: IY48658 (available approx. 10/15/03)
      APAR number for AIX 5.2.0: IY48657 (available approx. 10/29/03)

     An e-fix will be available shortly. The e-fix will be available
     from:

     ftp://ftp.software.ibm.com/aix/efixes/security/sendmail_4_efix.tar.Z

     This vendor statement will be updated when the e-fix becomes
     available.

Lotus

     This is a sendmail-specific issue that does not affect any Lotus
     products.

Network Appliance

     NetApp products are not vulnerable to this problem.

NetBSD

     NetBSD-current ships with sendmail 8.12.9 since June 1, 2003. The
     patch was applied on September 17, 2003. In the near future we
     would upgrade to sendmail 8.12.10.

     Our official releases, such as NetBSD 1.6.1, are also affected
     (they ship with older version of sendmail). They will be patched as
     soon as possible. We would issue NetBSD Security Advisory on this
     matter.

Openwall GNU/*/Linux

     Openwall GNU/*/Linux is not vulnerable. We ship Postfix, not
     Sendmail.

Red Hat

     Red Hat Linux and Red Hat Enterprise Linux ship with a Sendmail
     package vulnerable to these issues. Updated Sendmail packages are
     available along with our advisory at the URLs below. Users of the
     Red Hat Network can update their systems using the 'up2date' tool.

     Red Hat Linux:

      http://rhn.redhat.com/errata/RHSA-2003-283.html

     Red Hat Enterprise Linux:

      http://rhn.redhat.com/errata/RHSA-2003-284.html

The Sendmail Consortium

     The Sendmail Consortium recommends that sites upgrade to 8.12.10
     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/.

Sun

     Sun acknowledges that our recent release of sendmail 8.12.10 is
     affected by this issue on Solaris releases S7, S8 and S9.

     A Sun Alert for this issue will be isuued very soon which will then
     be available from:

      http://sunsolve.Sun.COM/pub-cgi/retrieve.pl?doc=fsalert/56860

     There are no patches available at this time. The Sun Alert will be
     updated with the patch information as it becomes available. Please
     refer to the Sun Alert when available, for more information.

SuSE

     SuSE products shipping sendmail are affected. Update packages that
     fix the vulnerability are being prepared and will be published
     shortly.

Appendix B. References

     * CERT/CC Vulnerability Note VU#784980 -
       <http://www.kb.cert.org/vuls/id/784980>
     * Michal Zalewski's post to BugTraq -
       <http://www.securityfocus.com/archive/1/337839>
     * Sendmail 8.12.10 - <http://www.sendmail.org/8.12.10.html>
     * Sendmail patch for 8.12.9 -
       <http://www.sendmail.org/patches/parse8.359.2.8>
     * Sendmail 8.12.10 announcement -
       <http://archives.neohapsis.com/archives/sendmail/2003-q3/0002.html
>
     * Sendmail Secure Install -
       <http://www.sendmail.org/secure-install.html>
   
     _________________________________________________________________

   This vulnerability was discovered by Michal Zalewski. Thanks to Claus
   Assmann and Eric Allman of Sendmail for their help in preparing this
   document.
     _________________________________________________________________

   Feedback can be directed to the author, Art Manion.
   ______________________________________________________________________

   This document is available from:
   http://www.cert.org/advisories/CA-2003-25.html
   ______________________________________________________________________

CERT/CC Contact Information

   Email: certcert.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

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     http://www.cert.org/

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   Copyright 2003 Carnegie Mellon University.

Revision History

   September 18, 2003: Initial release

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