[NT] Multiple Vulnerabilities in the AtHoc Toolbar for MSIE

From: SecuriTeam (support_at_securiteam.com)
Date: 01/23/05

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      Multiple Vulnerabilities in the AtHoc Toolbar for MSIE
    ------------------------------------------------------------------------

    SUMMARY

    Multiple vulnerabilities have been discovered in the
    <http://www.athoc.com/site/products/toolbar.asp> AtHoc toolbar that allows
    remote code execution through Internet Explorer when browsing to a
    specially crafted webpage. AtHoc sell a development suite which can allow
    a vendor to use their technology to create custom toolbars for their own
    clients.

    Among the most renound of AtHoc's toolbar clients are:
     * eBay
     * Accenture
     * ThomasRegister
     * ThomasRegional
     * Juniper Networks
     * WiredNews
     * CarFax
     * Agile PLM

    DETAILS

    The AtHoc toolbar comes with ActiveX component which exports a number of
    methods relating to the specifics of toolbar, such a skin settings,
    whether a debug log is to be kept, and numerous other options relating to
    customization.

    When attempting to provide an overly long 'skin name' to the SetSkin()
    method exported by the control, a stack based buffer overflows,
    overwriting a saved return address on the stack and eventually allowing
    arbitrary code to be executed.

    When the AtHoc toolbar is closed and re-started, a debug log is written
    containing various pieces of information relating to the success of
    certain operations which have been performed on the AtHoc toolbar during
    the users browsing session. One of the operations which is logged, is the
    setting of a 'base url', a value which is used by the toolbar when
    constructing absolute URLs for certain web related functionality. The
    SetBaseURL() function is used to set the base URL.

    If the url provided to the function is not valid, the URL is logged by the
    toolbar in the debug log, which is stored in the root of the drive on
    which the toolbar is installed. The code which writes the invalid base URL
    to the debug log is vulnerable to a format string attack which can
    overwrite arbitrary dwords in memory with arbitrary values. It is possible
    to overwrite saved return addresses, function pointers, string pointers
    and more to easily gain control over the execution flow of the process,
    thus allowing arbitrary code execution.

    The vulnerable component is marked safe for scripting by default, thereby
    allowing the dangerous functionality to be accessed with little user
    interaction.

    Fix Information:
    AtHoc has fixed these vulnerabilities and has advised the various vendors
    to update their toolbars to use the latest components. These fixed
    toolbars can be downloaded from the vendors respective websites.

    ADDITIONAL INFORMATION

    The information has been provided by <mailto:nisr@nextgenss.com>
    NGSSoftware Insight Security Research.
    The original article can be found at:
    <http://www.ngssoftware.com/advisories/athoc-01full.txt>
    http://www.ngssoftware.com/advisories/athoc-01full.txt

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