-----BEGIN PGP SIGNED MESSAGE----- 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: email@example.com 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 firstname.lastname@example.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 -----BEGIN PGP SIGNATURE----- Version: PGP 6.5.8 iQCVAwUBPoX5XGjtSoHZUTs5AQHvjgQAqTy3GQnszPHtUnUBX7VDM4NKSesFHHvC 2JmDAMPYmCO2b32xvWDmMcWdPhOBmJLB2o6zv7mRWX1K0B1GN5TBErIii6dxTaDD OAUNjirMGdTr+WnxIjdk0gj57JbOU6ZdHHcAijG5SE/dZq4sMrOCGEAMJTVNDzYp BtHbFwDeLEY= =dgBI -----END PGP SIGNATURE-----
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