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Summary
  • A vulnerability in Cisco WebEx browser extensions could allow an unauthenticated, remote attacker to execute arbitrary code with the privileges of the affected browser on an affected system. This vulnerability affects the browser extensions for Cisco WebEx Meetings Server and Cisco WebEx Centers (Meeting Center, Event Center, Training Center, and Support Center) when they are running on Microsoft Windows.

    The vulnerability is due to a design defect in an application programing interface (API) response parser within the plugin. An attacker that can convince an affected user to visit an attacker-controlled web page or follow an attacker-supplied link with an affected browser could exploit the vulnerability.  If successful, the attacker could execute arbitrary code with the privileges of the affected browser.

    Cisco has released software updates for Google Chrome, Firefox, and Internet Explorer that address this vulnerability. There are no workarounds that address this vulnerability.

    This advisory is available at the following link:
    https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170124-webex

Affected Products
  • Vulnerable Products

    This vulnerability affects Cisco WebEx extensions and plugins for Windows when running on most supported browsers. The affected browsers are Google Chrome, Mozilla Firefox, and Internet Explorer for Windows.

    The following versions of the Cisco WebEx browser extensions are affected by the vulnerability described in this document:

    • Versions prior to 1.0.7 of the Cisco WebEx Extension on Google Chrome
    • Versions prior to 106 of the ActiveTouch General Plugin Container on Mozilla Firefox
    • Versions prior to the first fixed version of the GpcContainer Class ActiveX control plugin on Internet Explorer – See the Fixed Software section
    • Versions prior to 2.1.0.10 of the Download Manager ActiveX control plugin on Internet Explorer

    Customers can determine which versions of the Cisco WebEx extensions are being utilized by following the steps listed below:

    Google Chrome
    Cisco WebEx Extension for Google Chrome version 1.0.7 was released on January 26, 2017, and contains a fix for this vulnerability. Chrome users can ensure they are using the fixed version of the Cisco WebEx Extension for Google Chrome by doing the following:

    1. In Chrome, open the Settings page
    2. Click Extensions

    The extension version is listed next to the Cisco WebEx Extension name.

    The Cisco WebEx Extension for Google Chrome identification string, which organizations can use to identify hosts that contain the plugin, is the following:

    Jlhmfgmfgeifomenelglieieghnjghma

    Mozilla Firefox
    Version 106 of the ActiveTouch General Plugin Container for Mozilla Firefox was released on January 28, 2017, and contains a fix for this vulnerability. Mozilla users can ensure they are using the fixed version of the ActiveTouch General Plugin Container for Mozilla by:

    1. Clicking the menu button (three horizontal bars on the upper right of the application) and selecting Add-ons
    2. In the Add-ons Manager tab, click the Plugins panel
    3. Locate the ActiveTouch General Plugin Container in the list of Plugins and click on the Morelink to obtain the version information
    The Cisco WebEx NPAPI Plugin for Mozilla Firefox identification string, which organizations can use to identify hosts that contain the plugin, is the following:

    atgpccontrol

    Microsoft Internet Explorer
    Versions of the Cisco WebEx Plugin for Microsoft Internet Explorer were released on January 28, 2017, and contain a fix for this vulnerability. The registered name of the plugin in Internet Explorer may differ based on the installation method used for the plugin. The fixed version of the plugin depends on the version of Cisco WebEx that provided the update. The update may have been applied either via the web when joining a WebEx meeting or by a local update of the client via an MSI file. Internet Explorer users can ensure they are using the fixed version of the plugin for Internet Explorer by:

    1. In Internet Explorer, select the Tools button
    2. Select Manage add-ons
    3. Select All add-ons from the Show drop-down menu
    4. Select either Download Manager or GpcContainer Class add-on under Cisco WebEx LLC

    The version number is displayed at the bottom of the Manage Add-ons window. See the table of fixed plugin versions in the Fixed Software section of this advisory.

    The Cisco WebEx ActiveX Plugin for Microsoft Internet Explorer Class ID (CLSID), which organizations can use to identify hosts that contain the plugin, is the following:

    E06E2E99-0AA1-11D4-ABA6-0060082AA75C

    Products Confirmed Not Vulnerable

    No other Cisco products are currently known to be affected by this vulnerability.

    Cisco WebEx Productivity Tools are not affected by this vulnerability.

    Cisco has confirmed that this vulnerability does not affect Cisco WebEx browser extensions for Mac or Linux, or Cisco WebEx on Microsoft Edge.

Workarounds
  • There are no workarounds that address this vulnerability. However, administrators and users of Windows 10 systems may utilize Microsoft Edge to join and participate in WebEx sessions as Microsoft Edge is not affected by this vulnerability. Additionally, administrators and users can remove all WebEx software from a Windows system by using the Meeting Services Removal Tool, which is available from https://help.webex.com/docs/DOC-2672.

    Customers who currently have web proxies or web gateways in their environment can create a URL filtering policy to block web requests matching the following condition:

    URL requests containing the string pattern « cwcsf-nativemsg-iframe-43c85c0d-d633-af5e-c056-32dc7efc570b.html »
    and
    URL hostname not matching the known customer’s WebEx site URL (e.g. company.webex.com in https://company.webex.com/cwcsf-nativemsg-iframe-43c85c0d-d633-af5e-c056-32dc7efc570b.html)

Fixed Software
  • Cisco has released free software updates that address the vulnerability described in this advisory. Customers may only install and expect support for software versions and feature sets for which they have purchased a license. By installing, downloading, accessing, or otherwise using such software upgrades, customers agree to follow the terms of the Cisco software license:
    http://www.cisco.com/en/US/docs/general/warranty/English/EU1KEN_.html

    Additionally, customers may only download software for which they have a valid license, procured from Cisco directly, or through a Cisco authorized reseller or partner. In most cases this will be a maintenance upgrade to software that was previously purchased. Free security software updates do not entitle customers to a new software license, additional software feature sets, or major revision upgrades.

    When considering software upgrades, customers are advised to regularly consult the advisories for Cisco products, which are available from the Cisco Security Advisories and Alerts page, to determine exposure and a complete upgrade solution.

    In all cases, customers should ensure that the devices to upgrade contain sufficient memory and confirm that current hardware and software configurations will continue to be supported properly by the new release. If the information is not clear, customers are advised to contact the Cisco Technical Assistance Center (TAC) or their contracted maintenance providers.