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             AUSCERT External Security Bulletin Redistribution

           ESB-2004.0283 -- iDEFENSE Security Advisory 04.15.04
    RealNetworks Helix Universal Server Denial of Service Vulnerability
                               16 April 2004

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        AusCERT Security Bulletin Summary
        ---------------------------------

Product:                RealNetworks Helix Universal Server
Publisher:              iDEFENSE
Operating System:       Solaris
                        Windows 2000
                        Linux
                        HP-UX
                        AIX
                        Tru64
                        FreeBSD
Impact:                 Denial of Service
Access Required:        Remote
CVE Names:              CAN-2004-0389

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RealNetworks Helix Universal Server Denial of Service Vulnerability

iDEFENSE Security Advisory 04.15.04
http://www.idefense.com/application/poi/display?type=vulnerabilities
February 15, 2004

I. BACKGROUND

RealNetworks Helix Universal Server is a universal digital media
delivery platform with industry leading performance, integrated content
distribution and Web services support. More information is available at
http://www.realnetworks.com.

II. DESCRIPTION

Remote exploitation of a denial of service (DoS) vulnerability in
RealNetworks, Inc.'s Helix Universal Server could allow an attacker to
restart and potentially disable the server.

The problem specifically exists in the handling of specially crafted GET
requests. The following sample requests will cause a null pointer
dereference, thereby causing the application to crash.

$ echo -e "GET_PARAMETER / RTSP/1.0\n\n" | nc -v localhost 554
$ echo -e "DESCRIBE / RTSP/1.0\nSession:\n\n" | nc -v localhost 554

If the server was started with specific options such as
'--no-crash-avoidance' or '--no-auto-restart', which is not the case in
the default installation, then the server will become inaccessible upon
receipt of the malicious requests.

III. ANALYSIS

Any unauthenticated remote attacker can exploit this vulnerability to
crash an affected server, thereby preventing legitimate usage.

Exploit code for this issue does not exist but is not necessary as the
issue is trivially exploited.

IV. DETECTION

iDEFENSE has confirmed the existence of this vulnerability in versions
9.0.2 for Linux and version 9.0.1 for Windows.

V. WORKAROUND

Ensure that the server options '--no-crash-avoidance' and
'--no-auto-restart' are not enabled.

VI. VENDOR RESPONSE

"Both issues have been secured in the 9.03 release of the server."

VII. CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CAN-2004-0389 to this issue. This is a candidate for inclusion in
the CVE list (http://cve.mitre.org), which standardizes names for
security problems.

VIII. DISCLOSURE TIMELINE

December 8, 2003    Exploit acquired by iDEFENSE
January 24, 2004    iDEFENSE clients notified
January 26, 2004    Initial vendor notification
April 15, 2004      Public disclosure

IX. CREDIT

Anonymous submission

Get paid for vulnerability research
http://www.idefense.com/poi/teams/vcp.jsp

X. LEGAL NOTICES

Copyright (c) 2004 iDEFENSE, Inc.

Permission is granted for the redistribution of this alert
electronically. It may not be edited in any way without the express
written consent of iDEFENSE. If you wish to reprint the whole or any
part of this alert in any other medium other than electronically, please
email customerservice@idefense.com for permission.

Disclaimer: The information in the advisory is believed to be accurate
at the time of publishing based on currently available information. Use
of the information constitutes acceptance for use in an AS IS condition.
There are no warranties with regard to this information. Neither the
author nor the publisher accepts any liability for any direct, indirect,
or consequential loss or damage arising from use of, or reliance on,
this information.

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