************************************************************************** Security Bulletin 9625 DISA Defense Communications System December 10, 1996 Published by: DISN Security Coordination Center (SCC@NIC.DDN.MIL) 1-(800) 365-3642 DEFENSE INFORMATION SYSTEM NETWORK SECURITY BULLETIN The DISN SECURITY BULLETIN is distributed by the DISN SCC (Security Coordination Center) under DISA contract as a means of communicating information on network and host security exposures, fixes, and concerns to security and management personnel at DISN facilities. Back issues may be obtained via FTP (or Kermit) from NIC.DDN.MIL [192.112.36.5] using login="anonymous" and password="guest". The bulletin pathname is scc/sec-yynn (where "yy" is the year the bulletin is issued and "nn" is a bulletin number, e.g. scc/sec-9544.txt). These are also available at our WWW site, http://nic.ddn.mil. ************************************************************************** + - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - + ! ! ! The following important advisory was issued by the Automated ! ! Systems Security Incident Support Team (ASSIST) and is being ! ! relayed unedited via the Defense Information Systems Agency's ! ! Security Coordination Center distribution system as a means ! ! of providing DISN subscribers with useful security information. ! ! ! + - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - + -----BEGIN PGP SIGNED MESSAGE----- <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> Automated Systems Security Incident Support Team _____ ___ ___ _____ ___ _____ | / /\ / \ / \ | / \ | | / Integritas / \ \___ \___ | \___ | | < et /____\ \ \ | \ | | \ Celeritas / \ \___/ \___/ __|__ \___/ | |_____\ <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> Bulletin 96-23 Release date: December 10, 1996, 12:30 PM EST (GMT -5) SUBJECT: stmpd-SIGHUP sendmail vulnerability SUMMARY: Sendmail versions 8.7.x to 8.8.2 contain serious vulnerabilities BACKGROUND: The sendmail vulnerabilities described in this bulletin were originally released and made public by the Australian Computer Emergency Response Team. IMPACT: Allows local users to gain root privileges. RECOMMENDED SOLUTIONS: ASSIST recommmends following the instructions in Section I of the AUSCERT advisory found below. <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> [Beginning of the AUSCERT advisory] =========================================================================== AA-96.10 AUSCERT Advisory smtpd-SIGHUP sendmail vulnerability 18 November 1996 Last Revised: -- - - - --------------------------------------------------------------------------- AUSCERT has received information that sendmail versions 8.7.x to 8.8.2 (inclusive) contain a serious security vulnerability. This vulnerability may allow local users to gain root privileges. Exploit details involving this vulnerability have been widely distributed. AUSCERT recommends that sites takes the steps outlined in Section 3 as soon as possible. - - --------------------------------------------------------------------------- 1. Description A vulnerability exists in all versions of sendmail from 8.7.x to 8.8.2 that allows local users to gain root privileges. A user can invoke sendmail in "daemon" mode by naming it to be "smtpd". Due to a coding error, this bypasses the usual check that only root can start the daemon. As of 8.7, sendmail will restart itself when it gets a SIGHUP signal. By manipulating the environment in which sendmail is run it is possible to force sendmail into executing an arbitrary program with root privileges. AUSCERT has been informed that sendmail versions prior to 8.8.x are no longer supported. Sites using older versions of sendmail will need to upgrade to the current version of sendmail. Sites can determine their version of sendmail by executing: % cat /dev/null | sendmail -d0 -bt | grep Version 2. Impact Local users can gain root privileges. 3. Workarounds/Solution AUSCERT recommends that sites upgrade to the current version of sendmail (see Section 3.1). 3.1 Upgrade to current version of sendmail Eric Allman has released a new version of sendmail (8.8.3) which fixes this vulnerability. There is no patch for 8.7.6. Sites running 8.7.x or previous versions will need to upgrade to 8.8.3. Sendmail 8.8.3 can be obtained from the following locations. ftp://ftp.sendmail.org/ucb/src/sendmail/ ftp://ftp.cert.dfn.de/pub/tools/net/sendmail/ ftp://ftp.auscert.org.au/pub/mirrors/ftp.cs.berkeley.edu/ucb/sendmail/ The MD5 checksum for this distribution is: MD5 (sendmail.8.8.3.patch) = 5b550b509b98912bea453b7a2c25d378 MD5 (sendmail.8.8.3.tar.gz) = 0cb58caae93a19ac69ddd40660e01646 MD5 (sendmail.8.8.3.tar.Z) = 7f7c5463012f8d7af368a79d417c72de ============================================================================ [End of AUSCERT advisory] ============================================================================ - ---------------------------------------------------------------------------- ASSIST wishes to thank AUSCERT and Eric Allman for their rapid response to this vulnerability and assistance in the preparation of this advisory. - ---------------------------------------------------------------------------- -----BEGIN PGP SIGNATURE----- Version: 2.6 iQCVAwUBMq1209H6sbnW3Io9AQH0NwQAvpRr5+tZDc/ReTlkWQ3pzdZRg3hD5TiW LvzI5jAFDg4MPRaEFydlc/0N056elobahoXeXuFzMvoKZA07I7me+rrMl5fsJOdi fzt4xgl2j6/tT1/Ur8kZSh43DB29fxJkxfQ0sNP0cpN5UR9xm8CKWTr7xUF3+kxo vg9/PEYAvas= =4tG+ -----END PGP SIGNATURE----- <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> ASSIST is an element of the Defense Information Systems Agency (DISA), Countermeasures, which provides service to the entire DoD community. Constituents of the DoD with questions about ASSIST or computer security issues, can contact ASSIST using one of the methods listed below. Non-DoD organizations/institutions, contact the Forum of Incident Response and Security Teams (FIRST) representative. To obtain a list of FIRST member organizations and their constituencies send an email to docserver@first.org with an empty "subject" line and a message body containing the line "send first-contacts". ASSIST Information Resources: To be included in the distribution list for the ASSIST bulletins, send your Milnet (Internet) e-mail address to assist-request@assist.mil. Back issues of ASSIST bulletins, and other security related information, are available from the ASSIST BBS at 703-607-4710, 327-4710, and through anonymous FTP from ftp.assist.mil (IP address 199.211.123.12). Note: ftp.assist.mil will only accept anonymous FTP connections from Milnet addresses that are registered with the NIC or DNS. If your system is not registered, you must provide your MILNET IP address to ASSIST before access can be provided. ASSIST Contact Information: PHONE: 800-357-4231 (or 703-607-4700 DSN 327), duty hours are 24 hours a day, 7 days a week, 365 days a year. ELECTRONIC MAIL: Send to assist@assist.mil. ASSIST BBS: Leave a message for the "sysop". ASSIST uses Pretty Good Privacy (PGP) as the digital signature mechanism for bulletins. PGP incorporates the RSAREF(tm) Cryptographic Toolkit under license from RSA Data Security, Inc. A copy of that license is available via anonymous FTP from net-dist.mit.edu (IP 18.72.0.3) in the file /pub/PGP/rsalicen.txt. In accordance with the terms of that license, PGP may be used for non-commercial purposes only. Instructions for downloading the PGP software can also be obtained from net-dist.mit.edu in the pub/PGP/README file. PGP and RSAREF may be subject to the export control laws of the United States of America as implemented by the United States Department of State Office of Defense Trade Controls. The PGP signature information will be attached to the end of ASSIST bulletins. Reference herein to any specific commercial product, process, or service by trade name, trademark manufacturer, or otherwise, does not constitute or imply its endorsement, recommendation, or favoring by ASSIST. 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-----END PGP PUBLIC KEY BLOCK----- **************************************************************************** * * * The point of contact for NIPRNET security-related incidents is the * * Security Coordination Center (SCC). * * * * E-mail address: SCC@NIC.DDN.MIL * * * * Telephone: 1-(800)-365-3642 * * * * NIC Help Desk personnel are available from 7:00 a.m.-7:00 p.m. EST, * * Monday through Friday except on federal holidays. * * * **************************************************************************** PLEASE NOTE: Some users outside of the DOD computing communities may receive DISN Security Bulletins. If you are not part of the DOD community, please contact your agency's incident response team to report incidents. Your agency's team will coordinate with DOD. 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 by sending email to docserver@first.org with an empty subject line and a message body containing the line: send first-contacts. This document was prepared as an service to the DOD community. Neither the United States Government nor any of their employees, makes any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial products, process, or service by trade name, trademark manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government. The opinions of the authors expressed herein do not necessarily state or reflect those of the United States Government, and shall not be used for advertising or product endorsement purposes.