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Category:   Application (Multimedia)  >   Helix Universal Server Vendors:   RealNetworks
RealNetworks Helix Universal Server Can Be Disabled With Cetain POST Request Content-Length Value
SecurityTracker Alert ID:  1011572
SecurityTracker URL:
CVE Reference:   CVE-2004-0774   (Links to External Site)
Date:  Oct 7 2004
Impact:   Denial of service via network
Fix Available:  Yes  Vendor Confirmed:  Yes  Exploit Included:  Yes  
Version(s): Helix Universal Server and prior versions; Also affects Helix Universal Mobile Server & Gateway, versions and prior
Description:   iDEFENSE reported a vulnerability in RealNetworks Helix Universal Server. A remote user can cause denial of service conditions.

It is reported that a remote user can send a specially crafted HTTP POST request with a Content-Length header set to '-1' to cause the target server to consume excessive memory and CPU resources. This will prevent the Helix service from processing any subsequent requests. The target service must be restarted to return to normal operations.

The vendor was notified on July 1, 2004.

The original advisory is available at:

Impact:   A remote user can cause the target service to become unavailable, requiring a restart to return to normal operations.
Solution:   The vendor has released a fixed version (

For Linux:

For Sun Solaris:

For Windows:

A fixed version of the Helix Mobile Universal Server and Gateway (10.04.1226) is available at:

Vendor URL: (Links to External Site)
Cause:   Exception handling error, Input validation error
Underlying OS:  Linux (Any), UNIX (Solaris - SunOS), Windows (Any)

Message History:   None.

 Source Message Contents

Subject:  iDEFENSE Security Advisory 10.07.04: RealNetworks Helix Server

RealNetworks Helix Server Content-Length Denial of Service Vulnerability

iDEFENSE Security Advisory 10.07.04:
October 7, 2004


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 Server could allow an attacker to restart and
potentially disable the server.

The problem specifically exists in the handling of specially crafted
POST requests. Generating a request with the Content-Length header set
to -1 triggers an integer handling error resulting in mass utilization
of memory and CPU time.


Any unauthenticated remote attacker can exploit this vulnerability,
which causes the affected system to utilize mass amounts of memory and
CPU time. The system will no longer be able to process future requests.

The affected server must be restarted in order to resume normal


iDEFENSE has confirmed the existence of this vulnerability in
RealNetworks Helix Server version 9.0.2 for Linux and version 9.0.3 for
Windows. It is suspected that earlier versions on both platforms are
vulnerable as well.


Usage of an inline application level filter can help mitigate risk of
exploitation by scanning for and filtering invalid Content-Length


"Customers are encouraged to upgrade their Server software to the latest
version, which contains a security patch."

RealNetworks has released binaries that guard against the described
vulnerability. The related advisory from RealNetworks is available at:


The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CAN-2004-0774 to this issue. This is a candidate for inclusion in
the CVE list (, which standardizes names for
security problems.


07/01/2004   Initial vendor notification
07/01/2004   iDEFENSE clients notified
08/05/2004   Initial vendor response
10/07/2004   Coordinated public Disclosure


The discoverer of this vulnerability wishes to remain anonymous.

Get paid for vulnerability research


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 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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