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Thread: CERT Advisory CA-2003-13 Multiple Vulnerabilities in Snort Preprocessors 04.17.2003

  1. #1
    Join Date
    Feb 2003

    CERT Advisory CA-2003-13 Multiple Vulnerabilities in Snort Preprocessors 04.17.2003

    I did not see this out here yet, so wanted to get this out quick, you are welcome to correct me please if someone was already vigilant on this one. I have not had time just yet to test the fix. Anyone else? Thanks.


    CERT Advisory CA-2003-13 Multiple Vulnerabilities in Snort Preprocessors

    Original release date: April 17, 2003
    Last revised: --
    Source: CERT/CC

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

    Systems Affected

    * Snort IDS, versions 1.8 through 2.0 RC1


    There are two vulnerabilities in the Snort Intrusion Detection System,
    each in a separate preprocessor module. Both vulnerabilities allow
    remote attackers to execute arbitrary code with the privileges of the
    user running Snort, typically root.

    I. Description

    The Snort intrusion detection system ships with a variety of
    preprocessor modules that allow the user to selectively include
    additional functionality. Researchers from two independent
    organizations have discovered vulnerabilities in two of these modules,
    the RPC preprocessor and the "stream4" TCP fragment reassembly

    For additional information regarding Snort, please see


    VU#139129 - Heap overflow in Snort "stream4" preprocessor (CAN-2003-0029)

    Researchers at CORE Security Technologies have discovered a remotely
    exploitable heap overflow in the Snort "stream4" preprocessor module.
    This module allows Snort to reassemble TCP packet fragments for
    further analysis.

    To exploit this vulnerability, an attacker must disrupt the state
    tracking mechanism of the preprocessor module by sending a series of
    packets with crafted sequence numbers. This causes the module to
    bypass a check for buffer overflow attempts and allows the attacker to
    insert arbitrary code into the heap.

    For additional information, please read the Core Security Technologies
    Advisory located at


    This vulnerability affects Snort versions 1.8.x, 1.9.x, and 2.0 prior
    to RC1. Snort has published an advisory regarding this vulnerability;
    it is available at


    VU#916785 - Buffer overflow in Snort RPC preprocessor (CAN-2003-0033)

    Researchers at Internet Security Systems (ISS) have discovered a
    remotely exploitable buffer overflow in the Snort RPC preprocessor
    module. Martin Roesch, primary developer for Snort, described the
    vulnerability as follows:

    When the RPC decoder normalizes fragmented RPC records, it
    incorrectly checks the lengths of what is being normalized against
    the current packet size, leading to an overflow condition. The RPC
    preprocessor is enabled by default.

    For additional information, please read the ISS X-Force advisory
    located at


    This vulnerability affects Snort versions 1.8.x through 1.9.1 and
    version 2.0 Beta.

    II. Impact

    Both VU#139129 and VU#916785 allow remote attackers to execute
    arbitrary code with the privileges of the user running Snort,
    typically root. In addition, it is not necessary for the attacker to
    know the IP address of the Snort device they wish to attack; merely
    sending malicious traffic where it can be observed by an affected
    Snort sensor is sufficient to exploit these vulnerabilities.

    III. Solution

    Upgrade to Snort 2.0

    Both VU#139129 and VU#916785 are addressed in Snort version 2.0, which
    is available at


    Binary-only versions of Snort are available from


    For information from other vendors that ship affected versions of
    Snort, please see Appendix A of this document.

    Disable affected preprocessor modules

    Sites that are unable to immediately upgrade affected Snort sensors
    may prevent exploitation of this vulnerability by commenting out the
    affected preprocessor modules in the "snort.conf" configuration file.

    To prevent exploitation of VU#139129, comment out the following line:

    preprocessor stream4_reassemble

    To prevent exploitation of VU#916785, comment out the following line:

    preprocessor rpc_decode: 111 32771

    After commenting out the affected modules, send a SIGHUP signal to the
    affected Snort process to update the configuration. Note that
    disabling these modules may have adverse affects on a sensor's ability
    to correctly process RPC record fragments and TCP packet fragments. In
    particular, disabling the "stream4" preprocessor module will prevent
    the Snort sensor from detecting a variety of IDS evasion attacks.

    Block outbound packets from Snort IDS systems

    You may be able limit an attacker's capabilities if the system is
    compromised by blocking all outbound traffic from the Snort sensor.
    While this workaround will not prevent exploitation of the
    vulnerability, it may make it more difficult for the attacker to
    create a useful exploit.

    Appendix A. - Vendor Information

    This appendix 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

    Apple Computer, Inc.

    Snort is not shipped with Mac OS X or Mac OS X Server.

    Ingrian Networks

    Ingrian Networks products are not susceptible to VU#139129 and
    VU#916785 since they do not use Snort.

    Ingrian customers who are using the IDS Extender Service Engine to
    mirror cleartext data to a Snort-based IDS should upgrade their IDS


    NetBSD does not include snort in the base system.

    Snort is available from the 3rd party software system, pkgsrc. Users
    who have installed net/snort, net/snort-mysql or net/snort-pgsql
    should update to a fixed version. pkgsrc/security/audit-packages can
    be used to keep up to date with these types of issues.

    Red Hat Inc.

    Not vulnerable. Red Hat does not ship Snort in any of our supported


    SGI does not ship snort as part of IRIX.


    Snort 2.0 has undergone an external third party professional security
    audit funded by Sourcefire.

    The CERT/CC acknowledges Bruce Leidl, Juan Pablo Martinez Kuhn, and
    Alejandro David Weil of Core Security Technologies for their discovery
    of VU#139129. We also acknowledge Mark Dowd and Neel Mehta of ISS
    X-Force for their discovery of VU#916785.

    Authors: Jeffrey P. Lanza and Cory F. Cohen.

    This document is available from:

    CERT/CC Contact Information

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    Fax: +1 412-268-6989
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    Revision History
    April 17, 2003: Initial release

    Version: PGP 6.5.8

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  2. #2
    Just a Virtualized Geek MrLinus's Avatar
    Join Date
    Sep 2001
    Redondo Beach, CA
    Again!? Wasn't that the same issue as before for the 1.9.0 version?
    Goodbye, Mittens (1992-2008). My pillow will be cold without your purring beside my head
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