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AUSCERT External Security Bulletin Redistribution
ESB-2002.662 -- CERT Advisory CA-2002-34
Buffer Overflow in Solaris X Window Font Service
26 November 2002
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AusCERT Security Bulletin Summary
---------------------------------
Product: XFS (X Window Font Service) Daemon
Vendor: Sun Microsystems
Operating System: Solaris 2.5.1
Solaris 2.6
Solaris 7
Solaris 8
Solaris 9
Platform: SPARC
Intel
Impact: Execute Arbitrary Code/Commands
Denial of Service
Access Required: Remote
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CERT Advisory CA-2002-34 Buffer Overflow in Solaris X Window Font Service
Original release date: November 25, 2002
Last revised: --
Source: CERT/CC
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: cert@cert.org
Phone: +1 412-268-7090 (24-hour hotline)
Fax: +1 412-268-6989
Postal address:
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______________________________________________________________________
NO WARRANTY
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_________________________________________________________________
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Copyright 2002 Carnegie Mellon University.
Revision History
November 25, 2002: Initial release
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