-----BEGIN PGP SIGNED MESSAGE----- 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 - * Michal Zalewski's post to BugTraq - * Sendmail 8.12.10 - * Sendmail patch for 8.12.9 - * Sendmail 8.12.10 announcement - * Sendmail Secure Install - _________________________________________________________________ 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: 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 September 18, 2003: Initial release -----BEGIN PGP SIGNATURE----- Version: PGP 6.5.8 iQCVAwUBP2nC8jpmH2w9K/0VAQFKwwP/Vagji3+avI6eb/5C++JCjjmL0Y+JrFmD 6DWgYsOVASDUO4bUyHYiAl2BM8s3owsprTRuKFl3WOf18h++qtTOOO1oeRt+bhqP 1q6ImxjAem7kM2f5e3xdArowptIlqMXFakQ2N3gHqyfXEcmgESrFcGNS8oCV20Y4 rriFRV/lvDU= =/mMy -----END PGP SIGNATURE-----