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Home » Hacking News » CERT Advisory CA-2002-34 Buffer Overflow in Solaris X Window Font Service

CERT Advisory CA-2002-34 Buffer Overflow in Solaris X Window Font Service

by Nikola Strahija on December 3rd, 2002 A complete revision history can be found at the end of this file.


Systems Affected

* Sun Microsystems Solaris 2.5.1 (Sparc/Intel)
* Sun Microsystems Solaris 2.6 (Sparc/Intel)
* Sun Microsystems Solaris 7 (Sparc/Intel)
* Sun Microsystems Solaris 8 (Sparc/Intel)
* Sun Microsystems Solaris 9 (Sparc)

Overview

The Solaris X Window Font Service (XFS) daemon (fs.auto) contains a
remotely exploitable buffer overflow vulnerability that could allow an
attacker to execute arbitrary code or cause a denial of service.

I. Description

A remotely exploitable buffer overflow vulnerability exists in the
Solaris X Window Font Service (XFS) daemon (fs.auto). Exploitation of
this vulnerability can lead to arbitrary code execution on a
vulnerable Solaris system. This vulnerability was discovered by ISS
X-Force.

The Solaris X Window Font Service (XFS) serves font files to clients.
Sun describes the XFS service as follows:

The X Font Server is a simple TCP/IP-based service that serves font
files to its clients. Clients connect to the server to request a
font set, and the server reads the font files off the disk and
serves them to the clients. The X Font Server daemon consists of a
server binary /usr/openwin/bin/xfs.

The XFS daemon is installed and running by default on all versions of
the Solaris operating system. Further information about this
vulnerability may be found in VU#312313.

http://www.kb.cert.org/vuls/id/312313

This vulnerability is also being referred to as CAN-2002-1317 by CVE.

Note this vulnerability is in the X Window Font Server, and not the
filesystem of a similar name.

II. Impact

A remote attacker can execute arbitrary code with the privileges of
the fs.auto daemon (typically nobody) or cause a denial of service by
crashing the service.

III. Solution

Apply a patch from your vendor

Appendix A contains information provided by vendors for this advisory.
As vendors report new information to the CERT/CC, we will 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.
Please contact your vendor directly.

Disable vulnerable service

Until patches can be applied, you may wish to disable the XFS daemon
(fs.auto). As a best practice, the CERT/CC recommends disabling all
services that are not explicitly required. On a typical Solaris
system, it should be possible to disable the fs.auto daemon by
commenting out the relevant entries in /etc/inetd.conf and then
restarting the inetd process.

Workarounds

Block access to port 7100/TCP at your network perimeter. Note that
this will not protect vulnerable hosts within your network perimeter.

Appendix A. - Vendor Information

NetBSD

NetBSD ships the xfs from XFree86, though its not on or used by
default.

OpenBSD

We do not have XFS.

SGI

We're not vulnerable to this.

Sun Microsystems

The Solaris X font server (xfs(1)) is affected by VU#312313 in the
following supported versions of Solaris:

Solaris 2.6
Solaris 7
Solaris 8
Solaris 9

Patches are being generated for all of the above releases. Sun will
be publishing a Sun Alert for this issue at the following location
shortly:

http://sunsolve.Sun.COM/pub-cgi/retrieve.pl?doc=fsalert/48879

The patches will be available from:

http://sunsolve.sun.com/securitypatch

Appendix B. - References

1. ISS X-Force Security Advisory: Solaris fs.auto Remote Compromise
Vulnerability -
http://bvlive01.iss.net/issEn/delivery/xforce/alertdetail.jsp?oid=
21541

2. Sun Cluster 3.0 U1 Data Services Developer's Guide, Chapter 6:
Sample DSDL Resource Type Implementation -
http://docs.sun.com/db/doc/806-7072/6jfvjtg1l?q=xfs&a=view

3. CERT/CC Vulnerability Note: VU#312313 -
http://www.kb.cert.org/vuls/id/312313

4. CVE reference number CAN-2002-1317. Information available at
http://cve.mitre.org
_________________________________________________________________

Internet Security Systems publicly reported this vulnerability.
_________________________________________________________________

Authors: Ian A. Finlay and Shawn V. Hernan.
______________________________________________________________________

This document is available from:
http://www.cert.org/advisories/CA-2002-34.html
______________________________________________________________________

CERT/CC Contact Information

Email: [email protected]
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.

CERT/CC personnel answer the hotline 08:00-17:00 EST(GMT-5) /
EDT(GMT-4) Monday through Friday; they are on call for emergencies
during other hours, on U.S. holidays, and on weekends.

Using encryption

We strongly urge you to encrypt sensitive information sent by email.
Our public PGP key is available from
http://www.cert.org/CERT_PGP.key

If you prefer to use DES, please call the CERT hotline for more
information.

Getting security information

CERT publications and other security information are available from
our web site
http://www.cert.org/

To subscribe to the CERT mailing list for advisories and bulletins,
send email to [email protected] Please include in the body of your
message

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* "CERT" and "CERT Coordination Center" are registered in the U.S.
Patent and Trademark Office.
______________________________________________________________________

NO WARRANTY
Any material furnished by Carnegie Mellon University and the Software
Engineering Institute is furnished on an "as is" basis. Carnegie
Mellon University makes no warranties of any kind, either expressed or
implied as to any matter including, but not limited to, warranty of
fitness for a particular purpose or merchantability, exclusivity or
results obtained from use of the material. Carnegie Mellon University
does not make any warranty of any kind with respect to freedom from
patent, trademark, or copyright infringement.
_________________________________________________________________

Conditions for use, disclaimers, and sponsorship information

Copyright 2002 Carnegie Mellon University.

Revision History
November 25, 2002: Initial release


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