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CERT Advisory CA-2001-31 Buffer Overflow in CDE Subprocess Control Service

   Original release date: November 12, 2001
   Last revised: --
   Source: CERT/CC

   A complete revision history can be found at the end of this file.

Systems Affected

     * Systems running CDE

Overview

   There is a remotely exploitable buffer overflow vulnerability in a
   library function used by the CDE Subprocess Control Service. This
   vulnerability could be used to crash the service or to execute
   arbitrary code with root privileges. This vulnerability is documented
   in VU#172583.

I. Description

   The Common Desktop Environment (CDE) is an integrated graphical user
   interface that runs on UNIX and Linux operating systems. The CDE
   Subprocess Control Service (dtspcd) is a network daemon that accepts
   requests from clients to execute commands and launch applications
   remotely. On systems running CDE, dtspcd is spawned by the Internet
   services daemon (typically inetd or xinetd) in response to a CDE
   client request. dtspcd is typically configured to run on port 6112/tcp
   with root privileges.

   For more information about CDE, see

          http://www.opengroup.org/cde/

          http://www.opengroup.org/desktop/faq/

   There is a remotely exploitable buffer overflow vulnerability in a
   shared library that is used by dtspcd. During client negotiation,
   dtspcd accepts a length value and subsequent data from the client
   without performing adequate input validation. As a result, a malicious
   client can manipulate data sent to dtspcd and cause a buffer overflow,
   potentially executing code with root privileges.

   The vulnerability was first reported to us in March 1999, and more
   recently by Internet Security Systems (ISS) X-Force. For more
   information, see

          http://www.kb.cert.org/vuls/id/172583

          http://xforce.iss.net/alerts/advise101.php

   This vulnerability has been assigned the identifier CAN-2001-0803 by
   the Common Vulnerabilities and Exposures (CVE) group:

          http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2001-0803

   Many common UNIX systems ship with CDE installed and enabled by
   default. To determine if your system is configured to run dtspcd,
   check for the following entries (may be wrapped):

     /etc/services

         dtspc 6112/tcp

     /etc/inetd.conf

         dtspc stream tcp nowait root /usr/dt/bin/dtspcd
         /usr/dt/bin/dtspcd

   Any system that does not run the CDE Subprocess Control Service is not
   vulnerable to this problem.

II. Impact

   An attacker can execute arbitrary code with root privileges.

III. Solution

Apply a patch

   Appendix A contains information from vendors who have provided
   information for this advisory. We will update the appendix as we
   receive more information. If a vendor's name does not appear, then the
   CERT/CC did not hear from that vendor. Please contact your vendor
   directly.

Limit access to vulnerable service

   Until patches are available and can be applied, you may wish to limit
   or block access to the Subprocess Control Service from untrusted
   networks such as the Internet. Using a firewall or other
   packet-filtering technology, block or restrict access to the port used
   by the Subprocess Control Service. As noted above, dtspcd is typically
   configured to listen on port 6112/tcp. It may be possible to use TCP
   Wrapper or a similar technology to provide improved access control and
   logging functionality for dtspcd connections. Keep in mind that
   blocking ports at a network perimeter does not protect the vulnerable
   service from the internal network. It is important to understand your
   network configuration and service requirements before deciding what
   changes are appropriate. TCP Wrapper is available from

          ftp://ftp.porcupine.org/pub/security/index.html

Appendix A. - Vendor Information

   This appendix contains information provided by vendors for this
   advisory. When vendors report new information to the CERT/CC, we
   update this section and note the changes in our revision history. If a
   particular vendor is not listed below, we have not received their
   comments.

Caldera, Inc.

   Caldera Open Unix and UnixWare are vulnerable. Caldera has released
   Security Advisory CSSA-2001-SCO.30 (URL wrapped):

          ftp://stage.caldera.com/pub/security/openunix/
          CSSA-2001-SCO.30/CSSA-2001-SCO.30.txt

Compaq Computer Corporation

   Case ID SSRT0782U
   Compaq has not been able to reproduce the problem identified in this
   advisory for any Compaq OS. However, with the information available,
   we are including a code change for Compaq's TRU64 UNIX that will
   further reduce any potential overflow vulnerability. This updated code
   will be announced when patches are available from the TRU64 UNIX FTP
   site and will be included in future releases of TRU64 UNIX. The TRU64
   UNIX FTP patch site is at:

          http://ftp.support.compaq.com/public/dunix/

   To subscribe to automatically receive future NEW Security Advisories
   from the Compaq's Software Security Response Team via electronic mail,
   use your browser select the URL:

          http://www.support.compaq.com/patches/mailing-list.shtml

   Select "Security and Individual Notices" for immediate dispatch
   notifications directly to your mailbox.
   To report new Security Vulnerabilities, send mail to:

          security-ssrtcompaq.com

Cray Inc.

   UNICOS, UNICOS/mk, and CrayTools are not vulnerable.

Fujitsu

   Fujitsu's UXP/V operating system is not vulnerable because it does not
   support any CDE components.

Hewlett-Packard Company

   The version of dtspcd supplied by HP has a buffer overflow. It is not
   clear whether this overflow can be exploited. To be safe HP is
   generating patches to fix this overflow on the assumption that it
   might be exploitable.

IBM Corporation

   IBM addressed a buffer overflow in CDE dtspcd in AIX 4.x around April
   1999. See the following APARs for more information (URLs wrapped):
   APAR IY06694:

          http://techsupport.services.ibm.com/aix/fixes/v4/X11/
          X11.Dt.rte.4.3.3.10.info

   APAR IX89419 (AIX 4.3.0):

          http://www-1.ibm.com/servlet/support/manager?rs=0&rt=0&
          org=apars&doc=29B5A5858069D8A2852567C90039978E
          http://techsupport.services.ibm.com/aix/fixes/v4/X11/
          X11.Dt.lib.4.3.2.5.info

   APAR IX89893 (AIX 4.2.0):

          http://www-1.ibm.com/servlet/support/manager?rs=0&rt=0&
          org=apars&doc=AAF008DAA07200B6852567CC0049B07D

   APAR IX89806 (AIX V4.1 BOS):

          http://www-1.ibm.com/servlet/support/manager?rs=0&rt=0&
          org=apars&doc=446F48D60A887FF0852567CA005C9920

The Open Group

   The Open Group maintains source code for the Common Desktop
   Environment (CDE). The Open Group is investigating this issue, and
   source licensees of The Open Group's CDE product can contact
   desktopopengroup.org for advice regarding this issue.

SGI

   SGI acknowledges the CDE vulnerabilities reported by CERT and is
   currently investigating. No further information is available at this
   time. For the protection of all our customers, SGI does not disclose,
   discuss or confirm vulnerabilities until a full investigation has
   occurred and any necessary patch(es) or release streams are available
   for all vulnerable and supported IRIX operating systems. Until SGI has
   more definitive information to provide, customers are encouraged to
   assume all security vulnerabilities as exploitable and take
   appropriate steps according to local site security policies and
   requirements. As further information becomes available, additional
   advisories will be issued via the normal SGI security information
   distribution methods including the wiretap mailing list.

          http://www.sgi.com/support/security/

Sun

   The Sun dtspcd daemon is vulnerable to this buffer overflow. Sun is
   generating patches to address this issue for all affected and
   supported versions of Solaris. Sun will be releasing a Sun Security
   Bulletin once the patches are officially released and publicly
   available. The patches will be available from:

          http://sunsolve.sun.com/securitypatch

   Sun Security Bulletins are available from:

          http://sunsolve.sun.com/security

Xi Graphics

   We have not been able to confirm whether we are vulnerable to this
   exploit, however the potential for a buffer overrun is present. We
   will provide a patch on our FTP site for DeXtop during the week of
   [November] 12th that addresses this issue.

Appendix B. - References

    1. http://www.kb.cert.org/vuls/id/172583
    2. http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2001-0803
    3. http://xforce.iss.net/alerts/advise101.php
    4. http://www.opengroup.org/cde/
    5. http://www.opengroup.org/desktop/faq/
     _________________________________________________________________
     _________________________________________________________________

   The CERT Coordination Center thanks Internet Security Systems (ISS)
   X-Force, who published an advisory on this issue.
     _________________________________________________________________

   Author: Art Manion
   ______________________________________________________________________

   This document is available from:
   http://www.cert.org/advisories/CA-2001-31.html
   ______________________________________________________________________

CERT/CC Contact Information

   Email: certcert.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.

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   Copyright 2001 Carnegie Mellon University.

   Revision History
November 12, 2001: initial release

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