Public Vulnerability Reports

RealNetworks Helix Universal Server Denial of Service Vulnerability



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


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/1.0nn" | nc -v localhost 554
$ echo -e "DESCRIBE / RTSP/1.0nSession:nn" | 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.


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.


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


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


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


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 (, which standardizes names for
security problems.


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Copyright © 2004 Verisign, Inc.

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