iDefense Security Advisory 02.01.10: RealNetworks RealPlayer 11 HTTP- Chunked Encoding Integer Overflow Vulnerability

From: iDefense Labs <>
Subject: iDefense Security Advisory 02.01.10: RealNetworks RealPlayer 11 HTTP- Chunked Encoding Integer Overflow Vulnerability

iDefense Security Advisory 02.01.10
Feb 01, 2010


RealPlayer is an application for playing various media formats,
developed by RealNetworks Inc. Since late 2003, Real Player has been
based on the open-source Helix Player. More information can be found at
the URLs shown. For more information, see the vendor's site found at the
following link.


Remote exploitation of an integer overflow vulnerability in RealNetworks
Inc.'s RealPlayer 11 could allow an attacker to execute arbitrary code
with the privileges of the affected service.

The vulnerability specifically exists in the handling of the 'chunked'
Transfer-Encoding method. This method breaks the file the server is
sending into 'chunks'. For each chunk, the server first sends the
length of the chunk in hexadecimal, followed by the chunk data. This is
repeated until there are no more chunks. The server then sends a chunk
length of zero (0) indicating the end of the transfer. When processing
these chunks, an integer overflow occurs, which results in a heap
overflow. This leads to the execution of arbitrary code.


Exploitation of this vulnerability results in the execution of arbitrary
code with the privileges of the user executing Real Player.

To be successful, an attacker must persuade a user to use Real Player to
view specially crafted media. This could be accomplished via a Web page
using the RealPlayer plug-in or a direct link to the malicious media.

It appears that the RealPlayer plug-in for Firefox uses the browser to
download files via HTTP. The RealPlayer chunked encoding processing is
not used in this scenario. However, RealPlayer does provide a
right-click context menu to open the document within RealPlayer itself.
As such, using Firefox does not prevent exploitation altogether.


iDefense has confirmed the existence of this vulnerability in RealPlayer
version 11 on Windows. A nightly build of RealPlayer for
Linux was also confirmed to be vulnerable. Previous versions do not
appear be affected.


iDefense is currently unaware of any workarounds for this issue.


RealNetworks has released a patch which addresses this issue.
Information about downloadable vendor updates can be found by clicking
on the URLs shown.


The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CVE-2009-4243 to this issue. This is a candidate for inclusion in
the CVE list (, which standardizes names for
security problems.


01/11/2008  Initial Contact
01/11/2009  Initial Response
02/01/2010  Coordinated public disclosure.


The discoverer of this vulnerability wishes to remain anonymous.

Get paid for vulnerability research

Free tools, research and upcoming events


Copyright  2010 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 e-mail 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.

Copyright © 1995-2020 All rights reserved.