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 running CDE
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.
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
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
This vulnerability has been assigned the identifier CAN-2001-0803 by the Common Vulnerabilities and Exposures (CVE) group:
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.
An attacker can execute arbitrary code with root privileges.
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
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 Open Unix and UnixWare are vulnerable. Caldera has released Security Advisory CSSA-2001-SCO.30 (URL wrapped):
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:
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:
Select "Security and Individual Notices" for immediate dispatch notifications directly to your mailbox. To report new Security Vulnerabilities, send mail to:
UNICOS, UNICOS/mk, and CrayTools are not vulnerable.
Fujitsu's UXP/V operating system is not vulnerable because it does not support any CDE components.
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 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:
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.22.214.171.124.info
APAR IX89893 (AIX 4.2.0):
APAR IX89806 (AIX V4.1 BOS):
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 firstname.lastname@example.org for advice regarding this issue.
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.
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:
Sun Security Bulletins are available from:
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
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Revision History November 12, 2001: initial release