Foundstone, Inc.

                        http://www.foundstone.com

                      "Securing the Dot Com World"



                           Security Advisory



                           Allaire's JRUN DoS



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FS Advisory ID:         FS-110100-17-JRUN



Release Date:           November 1, 2000



Product:                JRun 3.0



Vendor:                 Allaire Inc. (http://www.allaire.com)



Vendor Advisory:        http://www.allaire.com/security/



Type:                   Denial of Service attack



Severity:               High



Author:                 Shreeraj Shah (shreeraj.shah@foundstone.com)

                        Saumil Shah (saumil.shah@foundstone.com)

                        Stuart McClure (stuart.mcclure@foundstone.com)

                        Foundstone, Inc. (http://www.foundstone.com)



Operating Systems:      All operating systems



Vulnerable versions:    JRun 3.0



Foundstone Advisory:

http://www.foundstone.com/cgi-bin/display.cgi?Section_ID=13

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Description



        A denial of service vulnerability exists within the Allaire

        JRun 3.0 web application server which allows an attacker to

        bring down the JRun application server engine.



Details



        JRun3.0 is a Java application server, supporting Java Server

        Pages, Java servlets and other Java related technologies. The

        /servlet URL prefix is mapped as a handler for invoking

        servlets.



        Servlets are stored in a hierarchical manner and are accessed

        via a naming convention of the type:



           .. ... .



        Hence if a servlet called test is stored under com/site/test,

        it is invoked by the URL:



           http://site.running.jrun/servlet/com.site.test



        If a large string of dots is placed after the /servlet/ URL

        prefix, such as:



           http://site.running.jrun/servlet/................

           (hundreds of "."s)



        it gets interpreted as a very large tree of non-existent

        directories when looking for the servlet. This causes the

        JRun server engine to temporarily consume system resources at

        a high priority, and brings about a temporary denial of

        services for the JRun server engine. Other services do not

        get affected.



        If many such URL requests are made, the JRun server engine

        (specifically the javaw process) does not recover. All

        other JRun dependent requests get denied.



Proof of concept



        From a browser, make the following URL request:



        http://site.running.jrun/servlet/........... (many "."s)



Solution



        Follow the recommendations given in Allaire Security Bulletin

        ASB00-30, available at: http://www.allaire.com/security/



Credits



        We would also like to thank Allaire Inc. for their prompt

        reaction to this problem and their co-operation in heightening

        security awareness in the security community.



Disclaimer



        The information contained in this advisory is the copyright (C)

        2000 of Foundstone, Inc. and believed to be accurate at the time

        of printing, but no representation or warranty is given, express

        or implied, as to its accuracy or completeness. Neither the

        author nor the publisher accepts any liability whatsoever for

        any direct, indirect or conquential loss or damage arising in

        any way from any use of, or reliance placed on, this information

        for any purpose. This advisory may be redistributed provided that

        no fee is assigned and that the advisory is not modified in any

        way.