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TUCoPS :: Unix :: General :: n-049.txt

Snort RPC Preprocessing Vulnerability (CIAC N-049)


                       The U.S. Department of Energy
                   Computer Incident Advisory Capability
                           ___  __ __    _     ___
                          /       |     /_\   /
                          \___  __|__  /   \  \___

                             INFORMATION BULLETIN

                     Snort RPC Preprocessing Vulnerability
                   [Internet Security Systems Security Brief]

March 3, 2003 18:00 GMT                                           Number N-049
[Revised 5 March, 2003]
PROBLEM:       A buffer overflow flaw exists in the Snort RPC preprocessing
               code that is enabled by default.
PLATFORM:      Snort 1.8 (July 2001) up to and including Snort-Current (March
               3, 2003 1pm ET)
DAMAGE:        A remote attacker may exploit the buffer overflow condition to
               run arbitrary code on a Snort sensor with the privileges of the
               Snort IDS process (typically root).
SOLUTION:      Upgrade to Snort 1.9.1. If you are unable to upgrade, comment
               out the line in your snort.conf file that begins: 
                  preprocessor rpc_decode 
               and replace it with: 
                  #preprocessor rpc_decode
VULNERABILITY  The risk is HIGH. This vulnerability is especially dangerous
ASSESSMENT:    because it is not necessary to establish an actual connection
               to a RPC portmapper service to exploit this vulnerability.
[***** Start Internet Security Systems Security Brief *****]

Internet Security Systems Security Brief
March 3, 2003

Snort RPC Preprocessing Vulnerability


ISS X-Force has discovered a remotely exploitable buffer overflow
condition in Snort. Snort is an open source intrusion detection system. 
A buffer overflow flaw exists in Snort RPC preprocessing code that is
vulnerable to attack.


Remote attackers may exploit the buffer overflow condition to run
arbitrary code on a Snort sensor with the privileges of the Snort 
IDS process, which typically runs as the superuser. The vulnerable 
preprocessor is enabled by default. It is not necessary to establish 
an actual connection to a RPC portmapper service to exploit this 

Snort may be installed by default on some commercially available
network-security appliances. Remote attackers can exploit this 
vulnerability by directing the exploit towards any host on any 
network monitored by the Snort intrusion detection system. A successful 
attack can either crash the Snort sensor, or lead to complete remote 

Affected Versions:

Snort 1.8 (July 2001) up to and including Snort-Current (March 3,
2003 1pm ET)

For the complete ISS X-Force Security Advisory, please visit:


About Internet Security Systems (ISS)
Founded in 1994, Internet Security Systems (ISS) (Nasdaq: ISSX) is a
pioneer and world leader in software and services that protect
critical online resources from an ever-changing spectrum of threats 
and misuse.

Internet Security Systems is headquartered in Atlanta, GA, with
additional operations throughout the Americas, Asia, Australia,
Europe and the Middle East.

Copyright (c) 2003 Internet Security Systems, Inc. All rights
reserved worldwide.

Permission is hereby granted for the electronic redistribution of
this document. It is not to be edited or altered in any way without the
express written consent of the Internet Security Systems X-Force. If
you wish to reprint the whole or any part of this document in any
other medium excluding electronic media, please email for

Disclaimer: The information within this paper may change without
notice. Use of this information constitutes acceptance for use in an 
AS IS condition. There are NO warranties, implied or otherwise, with 
regard to this information or its use. Any use of this information 
is at the user's risk. In no event shall the author/distributor (Internet
Security Systems X-Force) be held liable for any damages whatsoever 
arising out of or in connection with the use or spread of this information.
X-Force PGP Key available on MIT's PGP key server and's key
server, as well as at
Please send suggestions, updates, and comments to: X-Force of Internet Security Systems, Inc.

[***** End Internet Security Systems Security Brief *****]

CIAC wishes to acknowledge the contributions of Internet Security Systems (X-Force) and SNORT organization for the
information contained in this bulletin.

CIAC, the Computer Incident Advisory Capability, is the computer
security incident response team for the U.S. Department of Energy
(DOE) and the emergency backup response team for the National
Institutes of Health (NIH). CIAC is located at the Lawrence Livermore
National Laboratory in Livermore, California. CIAC is also a founding
member of FIRST, the Forum of Incident Response and Security Teams, a
global organization established to foster cooperation and coordination
among computer security teams worldwide.

CIAC services are available to DOE, DOE contractors, and the NIH. CIAC
can be contacted at:
    Voice:    +1 925-422-8193 (7x24)
    FAX:      +1 925-423-8002
    STU-III:  +1 925-423-2604

Previous CIAC notices, anti-virus software, and other information are
available from the CIAC Computer Security Archive.

   World Wide Web:
   Anonymous FTP:

PLEASE NOTE: Many users outside of the DOE, ESnet, and NIH computing
communities receive CIAC bulletins.  If you are not part of these
communities, please contact your agency's response team to report
incidents. Your agency's team will coordinate with CIAC. The Forum of
Incident Response and Security Teams (FIRST) is a world-wide
organization. A list of FIRST member organizations and their
constituencies can be obtained via WWW at

This document was prepared as an account of work sponsored by an
agency of the United States Government. Neither the United States
Government nor the University of California nor any of their
employees, makes any warranty, express or implied, or assumes any
legal liability or responsibility for the accuracy, completeness, or
usefulness of any information, apparatus, product, or process
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recommendation or favoring by the United States Government or the
University of California. The views and opinions of authors expressed
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