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Security Services

RealNetworks RealPlayer CMediumBlockAllocator Integer Overflow Vulnerability



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 links.


Remote exploitation of an integer overflow vulnerability in RealNetworks Inc.'s Real Player could allow an attacker to execute arbitrary code with the privileges of the current user.

This problem specifically exists in the CMediumBlockAllocator::Alloc method. When calculating the size of a memory allocation, an integer overflow occurs. This leads to heap corruption, which can result in 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 or direct link to the malicious media.


iDefense has confirmed the existence of this vulnerability in Real Player versions 10.5 (build and 11 (build on Windows. Other versions may also be affected. RealNetworks has provided the following matrix of vulnerable products:

Windows RealPlayer 11.0.0 - 11.0.4
Windows RealPlayer 10.5 (,,
Mac RealPlayer 10
Linux RP10


iDefense is currently unaware of any effective workaround 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-2009-4248 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.

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Copyright © 2010 Verisign, Inc.

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