Public Vulnerability Reports

Real Networks RealPlayer URL Parsing Buffer Overflow Vulnerability



RealPlayer is an application for playing various media formats,
developed by RealNetworks Inc. For more information, visit


Remote exploitation of a buffer overflow in Version 10 of Real Networks'
RealPlayer could allow execution of arbitrary commands.

The vulnerability specifically exists in the handling of URLs with a
large number of period (".") characters. By creating a specially crafted
filename, it is possible to cause the execution of arbitrary code with
the permissions of the user that attempts to access it.


One method of exploiting this vulnerability is to place a .RAM file
(RealPlayer Presentation) containing a maliciously constructed URL on a
web server and send an e-mail to the target with a link containing the

It appears the vulnerability results from allocating an array of a fixed
size and then iterating through the URL looking for periods. As each one
is found, a pointer to it is stored in the array, and the current index
is incremented. No check seems to be done for writes to addresses
outside the array.


RealNetworks' RealPlayer 10 is confirmed vulnerable. Previous versions
of RealPlayer are also suspected to be vulnerable.


iDEFENSE is currently unaware of any effective workarounds for this

User awareness is the best defense against this class of attack. Users
should be aware of the existence of such attacks and proceed with
caution when following links from suspicious and/or unsolicited e-mail.


Real Networks recommends updating affected applications to the latest
version. Instructions for upgrading are contained in the vendor's
security advisory located at:


The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CAN-2004-0550 to this issue. This is a candidate for inclusion in
the CVE list (, which standardizes names for
security problems.


04/14/2004        Exploit discovered by iDEFENSE
05/12/2004        Initial vendor notification
05/12/2004        iDEFENSE clients notified
05/13/2004        Vendor response
06/10/2004        Coordinated public disclosure


Greg MacManus (iDEFENSE Labs) is credited with this discovery.

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Copyright © 2004 Verisign, Inc.

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