[Full-disclosure] iDEFENSE Security Advisory 06.23.05: RealNetworks RealPlayer RealText Parsing Heap Overflow Vulnerability

From: iDEFENSE Labs (labs-no-reply_at_idefense.com)
Date: 06/24/05

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    Date: Thu, 23 Jun 2005 20:39:58 -0400
    To: <bugtraq@securityfocus.com>, <vulnwatch@vulnwatch.org>, <full-disclosure@lists.grok.org.uk>

    RealNetworks RealPlayer RealText Parsing Heap Overflow Vulnerability

    iDEFENSE Security Advisory 06.23.05
    June 23, 2005


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


    Remote exploitation of a heap-based buffer overflow vulnerability in the

    RealText file format parser within various versions of RealNetworks
    Inc.'s RealPlayer could allow attackers to execute arbitrary code.

    The vulnerability specifically exists because of a string copying
    operating into a fixed size heap buffer using the sprintf function. The
    following function from /datatype/text/realtext/fileformat/rtffplin.cpp
    is the offending code:

    STDMETHODIMP CRealTextFileFormat::ReadDone()
                     if (pErrorMessages)
                        const char* pFilename = "[rt file]";
                        char* pTmp;
                        pTmp = new char[256];
                        sprintf(pTmp, /* Flawfinder: ignore */

                         "Version in \"%s\" is not recognized installed"

                         " RealText file format",pFilename);
                                          0, (const char*) pTmp, NULL);
                        delete [] pTmp;

    The variable pTmp points to 256 bytes of space on the heap. pFilename is

    a string pointer that points to data supplied in the RealText stream.
    When the sprintf is executed, the data is copied into the 256 byte heap
    buffer without any length checking, thus allowing a heap overflow to
    occur. Once the heap is overflown, an attacker can eventually write to
    arbitrary locations in memory, allowing for the execution of arbitrary


    Exploitation allows for arbitrary code execution as the user who opened
    the RealMedia file.

    Exploitation requires an attacker to craft a malicious RealMedia file
    that uses RealText and convince a user to open it. An attacker could
    also force a web browser to refresh and automatically load the RealMedia

    file from a normal web page under the attacker's control. In default
    installations of RealPlayer under Windows XP, Internet Explorer will not

    prompt the user for an action when encountering most RealMedia files. It

    will open the file without delay, thus providing an effective method of


    iDEFENSE Labs has confirmed that RealNetworks' RealPlayer 10.5 on Windows and RealPlayer 10 and on Linux are
    vulnerable. It is suspected that previous versions of RealPlayer are
    also vulnerable. It is also suspected that RealOne player is vulnerable.


    Although there is no way to completely protect yourself from this
    vulnerability, aside from removing the RealPlayer software, the
    following actions may be taken to minimize risk for automated

    Disable ActiveX controls and plugins, if not necessary for daily
    operations, using the following steps:

    1. In IE, click on Tools and select Internet Options from the drop-down
    2. Click the Security tab and the Custom Level button.
    3. Under ActiveX Controls and Plugins, then Run Activex Controls and
       Plugins, click the Disable radio button.


    The vendor has addressed this issue in the following security advisory:



    The Common Vulnerabilities and Exposures (CVE) project has assigned the
    name CAN-2005-1277 to this issue. This is a candidate for inclusion in
    the CVE list (http://cve.mitre.org), which standardizes names for
    security problems.


    04/26/2005 Initial vendor notification
    04/26/2005 Initial vendor response
    06/23/2005 Coordinated public disclosure


    The discoverer of this vulnerability wishes to remain anonymous.

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    Copyright (c) 2005 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 customerservice@idefense.com 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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