-----BEGIN PGP SIGNED MESSAGE----- ============================================================================= CERT(sm) Advisory CA-95:02 Original issue date: January 26, 1995 Last revised: November 21, 1996 Removed Appendices B and C. Updated Sec. B, par. 3 with the location of the current mail.local. A complete revision history is at the end of this file. Topic: Vulnerabilities in /bin/mail - ----------------------------------------------------------------------------- *** This advisory supersedes CA-91:01a and CA-91:13. *** There are vulnerabilities in some versions of /bin/mail. Section III below provides vendor-specific information and an alternative to /bin/mail. We will update this advisory as we receive additional information. Please check advisory files regularly for updates that relate to your site. - ----------------------------------------------------------------------------- I. Description Some versions of /bin/mail based on BSD 4.3 UNIX are vulnerable because of timing windows in the way /bin/mail uses publicly writable directories. II. Impact Local users (users that have an account on the system) can create or modify root-owned files on the system and can thereby gain unauthorized root access. III. Solutions Either install a patch from your vendor or replace /bin/mail with mail.local. A. Obtain the appropriate patch from your vendor and install it according to the instructions included with the patch. Below is a summary of the vendors listed in Appendix A of this advisory and the information they have provided. If your vendor's name is not on this list, please contact the vendor directly. Vendor or Source Status ---------------- ------------ Apple Computer, Inc. not vulnerable Berkeley SW Design, Inc. (BSDI) not vulnerable Data General Corp. not vulnerable Digital Equipment Corp. vulnerable, patches available FreeBSD not vulnerable Harris not vulnerable IBM not vulnerable NetBSD not vulnerable NeXT, Inc. not vulnerable Pyramid not vulnerable The Santa Cruz Operation (SCO) see note in Appendix A Solbourne (Grumman) vulnerable - contact vendor Sun Microsystems, Inc. SunOS 4.x vulnerable, patches available, patch revisions coming soon Solaris 2.x not vulnerable B. Replace /bin/mail with mail.local. If you cannot obtain a vendor-supplied replacement for /bin/mail, the CERT Coordination Center recommends using mail.local as a replacement for /bin/mail. Although the current version of mail.local is not a perfect solution, it addresses the vulnerabilities currently being exploited in /bin/mail. mail.local is now provided with the lastest version of sendmail. That version can be found at ftp://info.cert.org/pub/tools/sendmail/sendmail-latest* The original version of mail.local has been tested on SunOS 4.1 and Ultrix 4.X systems. Mail.local.c for BSD 4.3 systems, along with a README file containing installation instructions, can be found on the anonymous FTP servers listed below. Location -------- ftp://info.cert.org/pub/tools/mail.local/mail.local.c MD5 c0d64e740b42f6dc5cc54a2bc37c31b0 ftp://coast.cs.purdue.edu/pub/tools/unix/mail.local/mail.local.c MD5 c0d64e740b42f6dc5cc54a2bc37c31b0 ............................................................................... Appendix A: Vendor Information Below is information we have received from vendors who have patches available or upcoming for the vulnerabilities described in this advisory, as well as vendors who have confirmed that their products are not vulnerable. If your vendor's name is not in one of these lists, contact the vendor directly for information on whether their version of sendmail is vulnerable and, if so, the status of patches to address the vulnerabilities. NOT VULNERABLE - -------------- The following vendors have reported that their products are NOT vulnerable. Apple Computer, Inc. Berkeley SW Design, Inc. (BSDI) Data General Corp. Harris IBM NeXT, Inc. Pyramid The Santa Cruz Operation (SCO) - not vulnerable, but see note below Sun Microsystems, Inc. - Solaris 2.x (SunOS 4.x is vulnerable; see below) In addition, we have reports that the following products are NOT vulnerable. FreeBSD NetBSD VULNERABLE - ---------- We have reports that the following vendors' products ARE vulnerable. Patch information is provided below. - ----------------------------- Digital Equipment Corporation Vulnerable: DEC OSF/1 versions 1.2, 1.3, and 2.0 DEC ULTRIX versions 4.3, 4.3A, and 4.4 Obtain and install the appropriate patch according to the instructions included with the patch. The patch that corrects the /bin/mail problem in each case is part of a comprehensive Security Enhanced Kit that addresses other problems as well. This kit has been available since May 17, 1994. It is described in DEC security advisory #0505 and in CERT bulletin VB-94:02. 1. DEC OSF/1 Upgrade/install OSF/1 to a minimum of V2.0 and install Security Enhanced Kit CSCPAT_4061 v1.0. 2. DEC ULTRIX Upgrade/install ULTRIX to a minimum of V4.4 and install Security Enhanced Kit CSCPAT_4060 v1.0. Both kits listed above are available from Digital Equipment Corporation by contacting your normal Digital support channel or by request via DSNlink for electronic transfer. - ----------------------------- The Santa Cruz Operation (SCO) SCO's version of /bin/mail is not vulnerable to the problems mentioned in this advisory. SCO's /bin/mail is not setuid-root. However, SCO's /bin/mail has other security-related issues that are fixed by SCO's Support Level Supplement (SLS) uod392a. To get this: ftp: ftp.sco.COM:/SLS/uod392a.Z (compressed disk image) ftp.sco.COM:/SLS/uod392a.ltr.Z (cover letter) ftp.sco.COM:/SLS/README - ----------------------------- Solbourne Grumman System Support Corporation now performs all Solbourne software and hardware support. Please contact them for further information. ftp: ftp.nts.gssc.com phone: 1-800-447-2861 e-mail: support@nts.gssc.com - ----------------------------- Sun Microsystems, Inc. Current patches are listed below: SunOS Patch MD5 Checksum ------ ----- ------------ 4.1.3 100224-13.tar.Z 90a507017a1a40c4622b3f1f00ce5d2d 4.1.3U1 101436-08.tar.Z 0e64560edc61eb4b3da81a932e8b11e1 The patches can be obtained from local Sun Answer Centers and through anonymous FTP from ftp.uu.net in the /systems/sun/sun-dist directory. In Europe, the patches are available from mcsun.eu.net in the /sun/fixes directory. - --------------------------------------------------------------------------- The CERT Coordination Center thanks Eric Allman, Wolfgang Ley, Karl Strickland, Wietse Venema, and Neil Woods for their contributions to mail.local. - --------------------------------------------------------------------------- If you believe that your system has been compromised, contact the CERT Coordination Center or your representative in Forum of Incident Response and Security Teams (FIRST). If you wish to send sensitive incident or vulnerability information to CERT staff by electronic mail, we strongly advise that the e-mail be encrypted. The CERT Coordination Center can support a shared DES key, PGP (public key available via anonymous FTP on info.cert.org), or PEM (contact CERT staff for details). Internet E-mail: cert@cert.org Telephone: +1 412-268-7090 (24-hour hotline) CERT personnel answer 8:30 a.m.-5:00 p.m. EST(GMT-5)/EDT(GMT-4), and are on call for emergencies during other hours. Fax: +1 412-268-6989 CERT Coordination Center Software Engineering Institute Carnegie Mellon University Pittsburgh, PA 15213-3890 USA Past advisories, CERT bulletins, information about FIRST representatives, and other information related to computer security are available for anonymous FTP from info.cert.org. Copyright 1995, 1996 Carnegie Mellon University This material may be reproduced and distributed without permission provided it is used for noncommercial purposes and the copyright statement is included. CERT is a service mark of Carnegie Mellon University. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Revision history Nov. 21, 1996 Removed Appendices B & C. Sec. B, paragraph 3 - updated information about the location of mail.local. Aug. 30, 1996 Information previously in the README was inserted into the advisory, and URL formats were updated. June 09, 1995 Appendix A - corrected patch information from Sun. -----BEGIN PGP SIGNATURE----- Version: 2.6.2 iQCVAwUBMpSBxXVP+x0t4w7BAQHMUQP8DniFFLMKtR9w1j1NFE8DkoNIaAecAOye eSuLcAWPAhMeQzyerjvf1cAyMks38alz1YSnZHVDHab6boKIVt0CHfnBNlhU338X Rux9ID/dmfdl1JHWajDq7tSlPvAAeun99qd/4wYfmPyPSGU11NoNhbpH3QZvbNL3 1J+Xt/5Pcjc= =iHrV -----END PGP SIGNATURE-----