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CERT* Advisory CA-97.09
Original issue date: April 7, 1997
Last Revised: April 28, 1998
              Added vendor information for Silicon Graphics Inc.
              Corrected URL for obtaining RFCs. 

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


Topic: Vulnerability in IMAP and POP
- -----------------------------------------------------------------------------

The CERT Coordination Center has received reports of a vulnerability
in some versions of the University of Washington's implementation of
the Internet Message Access Protocol (IMAP) and Post Office Protocol
(POP). Information about this vulnerability has been publicly
distributed.

By exploiting this vulnerability, remote users can obtain unauthorized
root access.

As of the August 4, 1997 update, intrusions based on the exploitation of
this vulnerability continue to be reported to the CERT/CC.

The CERT/CC team recommends installing a patch if one is available or
upgrading to IMAP4rev1. Until you can do so, we recommend disabling the IMAP
and POP services at your site.

We will update this advisory as we receive additional information.
Please check our advisory files regularly for updates that relate to
your site.

- -----------------------------------------------------------------------------
I.   Description

     The current version of Internet Message Access Protocol (IMAP) supports
     both online and offline operation, permitting manipulation of remote
     message folders. It provides access to multiple mailboxes (possibly on
     multiple servers), and supports nested mailboxes as well as
     resynchronization with the server. The current version also provides a
     user with the ability to create, delete, and rename mailboxes. Additional
     details concerning the functionality of IMAP can be found in RFC 2060
     (the IMAP4rev1 specification) available from


                ftp://ftp.isi.edu/in-notes/rfc2060.txt

     The Post Office Protocol (POP) was designed to support offline mail
     processing. That is, the client connects to the server to download mail
     that the server is holding for the client. The mail is deleted from the
     server and is handled offline (locally) on the client machine.

     In the implementation of both protocols on a UNIX system, the server must
     run with root privileges so it can access mail folders and undertake some
     file manipulation on behalf of the user logging in. After login, these
     privileges are discarded. However, in at least the University of
     Washington's implementation a vulnerability exists in the way the login
     transaction is handled.  (See Appendix A for vendor information.) This
     vulnerability can be exploited to gain privileged access on the
     server. By preparing carefully crafted text to a system running a
     vulnerable version of these servers, remote users may be able to cause a
     buffer overflow and execute arbitrary instructions with root privileges.

     Information about this vulnerability has been widely distributed.

II.  Impact

     Remote users can obtain root access on systems running a vulnerable IMAP
     or POP server. They do not need access to an account on the system to do
     this.

III. Solution

     Install a patch from your vendor (see Section A) or upgrade to the latest
     version of IMAP (Section B).  If your POP server is based on the
     University of Washington IMAP server code, you should also upgrade to
     the latest version of IMAP. Until you can take one of these actions, you
     should disable services (Section C). In all cases, we urge you to take
     the additional precaution described in Section D.

  A. Obtain and install a patch from your vendor

     Below is a list of vendors who have provided information about this
     vulnerability. Details are in Appendix A of this advisory; we will update
     the appendix as we receive more information. If your vendor's name is not
     on this list, please contact your vendor directly.

        Berkeley Software Design, Inc. (BSDI)
        Carnegie Mellon University
        Cray Research
        Digital Equipment Corporation
        IBM Corporation
        Linux -  Caldera, Inc.
                 Debian
                 Red Hat
        Microsoft Corporation
        NetManage, Inc.
        Netscape
        QUALCOMM, Incorporated
        Silicon Graphics Inc.
        Sun Microsystems, Inc.
        University of Washington

  B. Upgrade to the latest version of IMAP

     An alternative to installing vendor patches is upgrading to IMAP4rev1,
     which is available from

        ftp://ftp.cac.washington.edu/mail/imap.tar.Z

     Please note that checksums change when files are updated.  The
     imap.tar.Z file can undergo frequent changes,  therefore the
     checksums have not been included here.

  C. Disable services

     Until you can take one of the above actions, temporarily disable the POP
     and IMAP services. On many systems, you will need to edit the
     /etc/inetd.conf file. However, you should check your vendor's
     documentation because systems vary in file location and the exact
     changes required (for example, sending the inetd process a HUP signal or
     killing and restarting the daemon).

     If you are not able to temporarily disable the POP and IMAP services,
     then you should at least limit access to the vulnerable services to
     machines in your local network. This can be done by installing the
     tcp_wrappers described in Section D, not only for logging but also for
     access control. Note that even with access control via tcp_wrappers, you
     are still vulnerable to attacks from hosts that are allowed to connect
     to the vulnerable POP or IMAP service.

 D.  Additional precaution

     Because IMAP or POP is launched out of inetd.conf, tcp_wrappers can be
     installed to log connections which can then be examined for suspicious
     activity. You may want to consider filtering connections at the firewall
     to discard unwanted/unauthorized connections.

     The tcp_wrappers tool is available in

        ftp://info.cert.org/pub/tools/tcp_wrappers/tcp_wrappers_7.5.tar.gz

        MD5 (tcp_wrappers_7.5.tar.gz) = 8c7a17a12d9be746e0488f7f6bfa4abb

     Note that this precaution does not address the vulnerability described
     in this advisory, but it is a good security practice in general.

...........................................................................

Appendix A - Vendor Information

Below is a list of the vendors who have provided information for this
advisory. We will update this appendix as we receive additional information.
If you do not see your vendor's name, the CERT/CC did not hear from that
vendor. Please contact the vendor directly.


Berkeley Software Design, Inc. (BSDI)
=====================================

  We're working on patches for both BSD/OS 2.1 and BSD/OS 3.0 for
  imap (which we include as part of pine).

Carnegie Mellon University
==========================

  Cyrus Server 1.5.2, with full IMAP4rev1 and pop3 capabilities, is NOT
  affected by this report and is NOT vulnerable.

Cray Research
=============

  Not vulnerable.

Digital Equipment Corporation
=============================

  This reported problem is not present for Digital's UNIX or
  Digital ULTRIX Operating Systems Software.

IBM Corporation
===============
 AIX 4.2.1 is the only version of AIX currently shipping with IMAP.
 Previous versions of AIX are not vulnerable.

  AIX 4.2.1
  ---------
    The following APAR will be available soon:

        APAR IX70263

  To Order
  --------
    APARs may be ordered using Electronic Fix Distribution (via FixDist)
    or from the IBM Support Center.  For more information on FixDist,
    reference URL:

       http://service.software.ibm.com/aixsupport/

    or send e-mail to aixserv@austin.ibm.com with a subject of "FixDist".


  IBM and AIX are registered trademarks of International Business Machines
  Corporation.

Linux Systems
=============

  Caldera, Inc.
  -------------
  On systems such as Caldera OpenLinux 1.0, an unprivileged user can
  obtain root access.

  As a temporary workaround, you can disable the POP and IMAP services
  in /etc/inetd.conf, and then kill and restart inetd.

  A better solution is to install the new RPM package that contains
  the fixed versions of the IMAP and POP daemons.  They are located
  on Caldera's FTP server (ftp.caldera.com):

        /pub/openlinux/updates/1.0/006/RPMS/imap-4.1.BETA-1.i386.rpm

        The MD5 checksum (from the "md5sum" command) for this package is:

        45a758dfd30f6d0291325894f9ec4c18

  This and other Caldera security resources are located at:

                http://www.caldera.com/tech-ref/security/

  Debian
  ------
  Debian linux is not vulnerable.  For more information see

        http://cgi.debian.org/www-master/debian.org/security.html

  Red Hat
  -------
  The IMAP servers included with all versions of Red Hat Linux have
  a buffer overrun which allow *remote* users to gain root access on
  systems which run them. A fix for Red Hat 4.1 is now available
  (details on it at the end of this note).

  Users of Red Hat 4.0 should apply the Red Hat 4.1 fix. Users of previous
  releases of Red Hat Linux are strongly encouraged to upgrade or simply
  not run imap. You can remove imap from any machine running with Red
  Hat Linux 2.0 or later by running the command "rpm -e imap", rendering
  them immune to this problem.

  All of the new packages are PGP signed with Red Hat's PGP key,
  and may be obtained from ftp.redhat.com:/updates/4.1. If
  you have direct Internet access, you may upgrade these packages on your
  system with the following commands:

  Intel:
  rpm -Uvh ftp://ftp.redhat.com/updates/4.1/i386/imap-4.1.BETA-3.i386.rpm

        MD5 (imap-4.1.BETA-3.i386.rpm) = 8ac64fff475ee43d409fc9776a6637a6

  Alpha:
  rpm -Uvh ftp://ftp.redhat.com/updates/4.1/alpha/imap-4.1.BETA-3.alpha.rpm

        MD5 (imap-4.1.BETA-3.alpha.rpm) = fd42ac24d7c4367ee51fd00e631cae5b

  SPARC:
  rpm -Uvh ftp://ftp.redhat.com/updates/4.1/sparc/imap-4.1.BETA-3.sparc.rpm

        MD5 (imap-4.1.BETA-3.sparc.rpm) = 751598aae3d179284b8ea4d7a9b78868

Microsoft
=========

Microsoft's Exchange POP and IMAP servers and Microsoft's Commericial
Internet System are not vulnerable

NetManage, Inc.
=========

NetManage's ZPOP pop server is not vulnerable.


Netscape
========

  Netscape's POP3/IMAP4 implementation is not vulnerable.

QUALCOMM Incorporated
======================

  Our engineers have examined the QPopper source code, which is based
  on source from UC Berkeley. They determined that QPopper is *NOT*
  vulnerable to a buffer overflow attack as described in CA-97.09.
  It strictly checks the size of messages before copying them into its
  buffer.

Silicon Graphics Inc.
=====================

Silicon Graphics Inc. Security Advisory, 19980302-01-I, provides the
following information:

  The Internet Mail Access Protocol (IMAP) & Post Office Protocol (POP)
  provide users with an alternative means to process and retrieve their email.

  A vulnerability has been discovered in IMAP4 & POP3 that allows remote
  users to obtain root access.

  Silicon Graphics sells and supports the Netscape Mail/Messaging Servers
  for IRIX which use IMAP4 & POP3 however, their implementations are not
  vulnerable to this issue and no further action is required.

  More information about Netscape product security can be found at the
  following URL:

  http://home.netscape.com/assist/security/


Sun Microsystems, Inc.
======================

The following patches have been released for CERT CA-97.09.

        105346-02 SIMS 2.0
        105347-02 SIMS 2.0_x86


University of Washington
========================

  This vulnerability has been detected in the University of Washington c-client
  library used in the UW IMAP and POP servers.  This vulnerability affects all
  versions of imapd prior to v10.165, all versions of ipop2d prior to 2.3(32),
  and all versions of ipop3d prior to 3.3(27).

  It is recommended that all sites using these servers upgrade to the
  latest versions, available in the UW IMAP toolkit:

        ftp://ftp.cac.washington.edu/mail/imap.tar.Z

  Please note that checksums change when files are updated.  The
  imap.tar.Z file can undergo frequent changes,  therefore the checksums
  have not been included here.

  This is a source distribution which includes imapd, ipop2d, ipop3d. and
  the c-client library.  The IMAP server in this distribution conforms with
  RFC2060 (the IMAP4rev1 specification).

  Sites which are not yet prepared to upgrade from IMAP2bis to IMAP4
  service may obtain a corrected IMAP2bis server as part of the latest
  (3.96) UW Pine distribution, available at:

        ftp://ftp.cac.washington.edu/pine/pine.tar.Z

        MD5 (pine.tar.Z) = 37138f0d1ec3175cf1ffe6c062c9abbf

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The CERT Coordination Center thanks the University of Washington's
Computing and Communications staff for information relating to this
advisory. We also thank Wolfgang Ley of DFN-CERT for his input. We
thank Matthew Wall of Carnegie Mellon University for additional
insightful feedback.

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If you believe that your system has been compromised, contact the CERT
Coordination Center or your representative in the Forum of Incident Response
and Security Teams (see http://www.first.org/team-info)


CERT/CC Contact Information
- ---------------------------
Email    cert@cert.org

Phone    +1 412-268-7090 (24-hour hotline)
                CERT personnel answer 8:30-5:00 p.m. EST(GMT-5) / EDT(GMT-4)
                and are on call for emergencies during other hours.

Fax      +1 412-268-6989

Postal address
         CERT Coordination Center
         Software Engineering Institute
         Carnegie Mellon University
         Pittsburgh PA 15213-3890
         USA

Using encryption
   We strongly urge you to encrypt sensitive information sent by email. We can
   support a shared DES key or PGP. Contact the CERT/CC for more information.
   Location of CERT PGP key
         ftp://info.cert.org/pub/CERT_PGP.key

Getting security information
   CERT publications and other security information are available from
        http://www.cert.org/
        ftp://info.cert.org/pub/

   CERT advisories and bulletins are also posted on the USENET newsgroup
        comp.security.announce

   To be added to our mailing list for advisories and bulletins, send
   email to
        cert-advisory-request@cert.org
   In the subject line, type
        SUBSCRIBE  your-email-address


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Copyright 1997, 1998 Carnegie Mellon University. Conditions for use,
disclaimers, and sponsorship information can be found in
http://www.cert.org/legal_stuff.html and
ftp://ftp.cert.org/pub/legal_stuff .  If you do not have FTP or web
access, send mail to cert@cert.org with "copyright" in the subject
line.

CERT is registered in the U.S. Patent and Trademark Office.


- ---------------------------------------------------------------------------

This file: ftp://info.cert.org/pub/cert_advisories/CA-97.09.imap_pop
           http://www.cert.org
               click on "CERT Advisories"

===========================================================================
UPDATES

April 8, 1997
- -------------

We have received requests for clarification.  The vulnerability
described in this advisory relates to certain server implementations
and is not in the protocol itself.  See Appendix A for vendor and
server information.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Revision history

Apr. 28, 1998 Added vendor information for Silicon Graphics Inc. 
              Corrected URL for obtaining RFCs.
Jan. 15, 1998 Updated vendor information for Sun Microsystems, Inc.
Sep. 26, 1997 Updated copyright statment
Aug. 27, 1997 Section III.A and Appendix A - added vendor information
              for IBM Corporation.
Aug 4, 1997   Clarifications in wording have been made to the introduction
              and paragraph 3 of the description section.
June 3, 1997  Section III.A and Appendix  - Added vendor information.
              for NetManage, Inc.
May 1, 1997   Section III.A and Appendix A - Added vendor information
              for Microsoft Corporation.
Apr 18, 1997  Section III.A and Appendix A - Added vendor information
              for Debian and Netscape.
Apr 11, 1997  Section III.B. - Removed checksum information for the
              imap.tar.Z distribution and added an explanation.
Apr 9, 1997   Appendix A - added vendor information for Digital Equipment
              Corporation and QUALCOMM Incorporated.
              Updated vendor information for Sun Microsystems, Inc.
              Added another name to acknowledgment.
Apr 08, 1997  Updates - Added clarification that the vulnerability
              is an implementation error and not an error in the protocol
              Appendix - added vendor information for Caldera and the
              Carnegie Mellon University Cyrus Server
              Acknowledgments - Added a name that was inadvertently left out


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