Buffer Overflow in Some Implementations of IMAP Servers

Original issue date: July 20, 1998
Last revised: March 08, 1999
Updated IMAP Server information for ISOCOR.

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

The CERT Coordination Center has received reports regarding a vulnerability in some implementations of IMAP servers.

The CERT/CC recommends that anyone running a vulnerable version of this software upgrade to the current vendor-recommended version. Until you can do so, we suggest disabling the vulnerable IMAP server.

We will update this advisory as we receive additional information. We encourage you to check our web site regularly for updates to this advisory that may relate to your site.

I. Description

The CERT Coordination Center has received reports regarding a buffer overflow in some implementations of IMAP servers. The overflow is in library code from the University of Washington IMAP server that handles SASL server-level authentication. This vulnerability is different from the one discussed in CERT Advisory CA-97.09.imap_pop. Information about this vulnerability has been posted to various public mailing lists and newsgroups.

All versions of the University of Washington IMAP server prior to the final (frozen, non-beta) version of imap-4.1 that support SASL server-level authentication are vulnerable. The vulnerability affects all University of Washington IMAP4rev1 servers prior to v10.234. Also, any v10.234 server that was distributed with Pine 4.0 or any imap-4.1.BETA is vulnerable.

Additionally, the vulnerability is present in other IMAP servers that use library code from the University of Washington IMAP server to handle SASL server-level authentication.

IMAP servers that share no code with the University of Washington server are not vulnerable.

Some operating systems ship with a vulnerable version of this software installed and enabled by default. Please refer to the Vendor Information section below for more information about your vendor.

II. Impact

Remote intruders can execute arbitrary commands under the privleges of the process running the vulnerable IMAP server. If the vulnerable IMAP server is running as root, remote intruders can gain root access.

III. Solution

  1. Determine if your version of imapd is vulnerable

    To determine if a system is vulnerable, first telnet to port 143 on that host. If it is running an IMAP server, the banner will show the version. For example:
    % telnet host.your.domain.com 143
    Connected to host.
    Escape character is '^]'.
    * OK host.your.domain.com IMAP4rev1 v10.190 server ready
    In the above example, the IMAP server is the University of Washington IMAP4rev1 v10.190. Since all University of Washington IMAP4rev1 servers prior to v10.234 are vulnerable, the server in the above example is vulnerable.
  2. Please consult the Vendor Information section below for information about other vulnerable IMAP servers.

  3. Install the most recent version of imapd

    Obtain and install the most recent version, or patch for your IMAP server. Appendix A contains input from vendors who have provided information for this advisory.
  4. Workaround

    If you are unable to upgrade to a version that is not vulnerable, we urge you to disable the IMAP server until you are able to address the problem.

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.

IMAP Server Vendors


   This does not affect the Cyrus imapd. Cyrus imapd shares no code with
   the University of Washington imapd.

Esys Corporation

   We are not affected by the problem described in the advisory. We do not
   ship any University of Washington based software at this time. We have
   never shipped any of the IMAP 4.x software from the University of


   No ISOCOR products are affected by this problem. The N-PLEX implementation
   shares no code with the University of Washington imapd.

Microsoft Corporation

   No Microsoft products are affected by this problem.

NEC Corporation

   The University of Washington imapd is shipped with our product
   "Mobilenet/IMAP" and so it is vulnerable.


   Netscape Messaging Server 3.55 and before are susceptible to this
   vulnerability. However, it should be noted that Netscape Messaging
   Server (any version) does NOT run as root and therefore, the exposure
   is much more limited than the University of Washington example.
   Regardless, we have released a patch available at 
   http://help.netscape.com/products/server/messaging which
   addresses this vulnerability.

Sun Microsystems

   Please refer to Sun Microsystems, Inc. Security Bulletin, "IMAP",
   Number: 00177, distributed October 2, 1998 for additional information
   relating to this vulnerability.
   Patches and Checksums are available to all Sun customers via World Wide
   Web at:
   Sun security bulletins are available via World Wide Web at:

University of Washington

   A security problem has been detected with the University of Washington
   IMAP server that is included in the Pine 4.00 distribution. This will
   be fixed in the forthcoming Pine 4.01 maintenance release. Until then,
   if you are using the UW IMAP server, please update it with the
   following distribution:
   This vulnerability affects all IMAP4rev1 servers prior to
   v10.234. v10.234 may or may not be vulnerable; if it came from Pine
   4.00 or from any imap-4.1.BETA then it is vulnerable. IMAP2bis
   servers are immune. This problem is also fixed in the imap-4.2
   toolkit, which is tentatively expected to be released in
   conjunction with Pine 4.01. Any IMAP4rev1 server whose version
   starts with "v11" will be immune.

Operating System Vendors

Berkeley Software Design, Inc.

   The version of IMAP shipped with BSD/OS 2.1 and 3.0/3.1 is the older
   version which does not include the vulnerability.
   The version of IMAP which will be included in the upcoming 4.0 release
   has been updated to include the security fixes.

Caldera Linux

   Caldera: releasing patched imap-4.1; will release imap-4.2 as soon as
            it becomes available.
   URL:     ftp://ftp.caldera.com/pub/OpenLinux/updates/1.2/010
   6df741b4217f03bf773b54509a7d283a  imap-4.1.BETA-5.i386.rpm
   d3526121c68b611524fc72746204d752  imap-4.1.BETA-5.src.rpm

Compaq Computer Corporation

   (c) Copyright 1994, 1995, 1996, 1997, 1998 Compaq Computer Corporation. 
   All rights reserved.
   SOURCE: Compaq Computer Corporation
           Compaq Services
           Software Security Response Team USA
   This reported problem is not present for the as shipped,
   Compaq's Digital ULTRIX or Compaq's Digital UNIX
   Operating Systems Software.
                             - Compaq Computer Corporation

Data General

   We are investigating. We will provide an update when our
   investigation is complete.


   FreeBSD does not ship default with imap. However, there is a version
   of imapd from Washington University in the FreeBSD ports collections,
   known as imap-uw.
   If anyone is using the imap port, we suggest fetching the latest revision
   of imap and manually install it, or wait until the FreeBSD port is updated
   and reinstall imap-uw using the ports system.
   You can check the ports status at:


   Our operating system, UXP/V, does not support imapd. Therefore, it is
   not vulnerable to the above vulnerability.

Hewlett-Packard Company

   HP does not ship the University of Washington IMAP server.

IBM Corporation

   The version of imapd shipped with AIX 4.2 and 4.3 is vulnerable.  We
   are currently working on the following fixes which will be available
     AIX 3.2.x:  imapd not shipped (not vulnerable)
     AIX 4.1.x:  imapd not shipped (not vulnerable)
     AIX 4.2.x:  IX80446
     AIX 4.3.x:  IX80447
   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:
     or send e-mail to aixserv@austin.ibm.com with a subject of "FixDist".
   IBM and AIX are registered trademarks of International Business Machines


   NetBSD does not ship the UW imapd daemon in its standard or development
   operating system releases. Our optional package system also does not
   include it at this time.


   OpenBSD has never shipped an imap daemon.

Red Hat Linux

   Serious security problems have been found in all versions of imap shipped
   with Red Hat Linux. If "rpm -q imap" shows that imap is installed on
   your system, please upgrade to these new imap releases immediately, or
   remove imap by running "rpm -e imap". Note that Red Hat's imap package
   also provides a POP server, so only remove it if you don't need to provide
   POP services.
   Thanks to everyone who helped find these problems, Olaf Kirch in particular.
   Red Hat 5.0 and 5.1
   rpm -Uvh ftp://ftp.redhat.com/updates/5.0/i386/imap-4.1.final-1.i386.rpm
   rpm -Uvh ftp://ftp.redhat.com/updates/5.0/alpha/imap-4.1.final-1.alpha.rpm
   rpm -Uvh ftp://ftp.redhat.com/updates/5.0/sparc/imap-4.1.final-1.sparc.rpm
   Red Hat 4.2
   rpm -Uvh ftp://ftp.redhat.com/updates/4.2/i386/imap-4.1.final-0.i386.rpm
   rpm -Uvh ftp://ftp.redhat.com/updates/4.2/alpha/imap-4.1.final-0.alpha.rpm
   rpm -Uvh ftp://ftp.redhat.com/updates/4.2/sparc/imap-4.1.final-0.sparc.rpm

The Santa Cruz Operation, Inc.

   The following SCO products are vulnerable:
   - SCO UnixWare 7
   SCO OpenServer 5.0, SCO CMW+ 3.0, SCO Open Desktop/Open Server 3.0,   and
   UnixWare 2.1 is not vulnerable as University of Washington imapd   is not
   included in these platforms.
   Binary versions of University of Washington imapd will be available   
   shortly from the SCO ftp site:
   ftp://ftp.sco.com/SSE/sse014.ltr - cover letter
   ftp://ftp.sco.com/SSE/sse014.tar.Z - replacement binaries
   This fix is a binary for the following SCO operating systems:
   - SCO UnixWare 7
   For the latest security bulletins and patches for SCO products,
   please refer to http://www.sco.com/security/.

Silicon Graphics Inc.

   Please refer to Silicon Graphics Inc. Security Advisory, "University
   of Washington imapd daemon Vulnerability," Number: 19980802-01-I,
   distributed August 6, 1998 for additional information relating to this
   The primary SGI anonymous FTP site for security information and patches
   is sgigate.sgi.com (  Security information and patches
   are located under the directories ~ftp/security and ~ftp/patches,
   respectively. The Silicon Graphics Security Headquarters Web page is
   accessible at the URL http://www.sgi.com/Support/security/security.html.

The CERT Coordination Center thanks Olaf Kirch of Caldera Linux for discovering and reporting the vulnerability. Additionally, we would like to thank Mark Crispin and Lori Stevens of the University of Washington for providing technical details and support in the development of the advisory.

Copyright 1998 Carnegie Mellon University.

Revision History
Mar. 08, 1999  Updated IMAP Server information for ISOCOR.
Nov. 16, 1998  Updated patch information for Sun Microsystems, Inc.
Sept. 4, 1998  Added vendor information for Silicon Graphics, Inc.
Aug. 14, 1998  Added vendor information for Microsoft Corporation.