[c-nsp] Cisco Security Advisory: Cisco ASA 5500 Series Adaptive Security Appliance Clientless VPN ActiveX Control Remote Code Execution Vulnerability

Wed Mar 14 12:16:48 EDT 2012

The Cisco Clientless VPN solution as deployed by Cisco ASA 5500
Series Adaptive Security Appliances (Cisco ASA) uses an ActiveX
control on client systems to perform port forwarding operations.
Microsoft Windows-based systems that are running Internet Explorer or
another browser that supports Microsoft ActiveX technology may be
affected if the system has ever connected to a device that is running
the Cisco Clientless VPN solution. A remote, unauthenticated attacker
who could convince a user to connect to a malicious web page could
exploit this issue to execute arbitrary code on the affected machine
with the privileges of the web browser.

The affected ActiveX control is distributed to endpoint systems by
Cisco ASA.  However, the impact of successful exploitation of this
vulnerability is to the endpoint system only and does not compromise
Cisco ASA devices.

Cisco has released free software updates that address this
vulnerability.

Workarounds that mitigate this vulnerability are available.

This advisory is available at the following link:

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20120314-asaclient

Affected Products
=================

Cisco Clientless VPN is a feature available on Cisco ASA 5500 Series
Adaptive Security Appliances.

Vulnerable Products
+------------------

Cisco ASA 5500 Series Adaptive Security Appliances that are running
one of the following versions contain the affected ActiveX component:

    +---------------------------------------------------------------+
    |Affected Version                              |Affected Release|
    |----------------------------------------------+----------------|
    | Cisco Adaptive Security Appliance Software   |7.1             |
    |7.x                                           |7.2             |
    |----------------------------------------------+----------------|
    |                                              |8.0             |
    |                                              |8.1             |
    | Cisco Adaptive Security Appliance Software   |8.2             |
    |8.x                                           |8.3             |
    |                                              |8.4             |
    |                                              |8.6             |
    +---------------------------------------------------------------+

    Note: Cisco ASA Software version 7.0 and 7.1 have reached end of
    software maintenance.  Customers who are using Cisco ASA Software
    version 7.0 or 7.1 should contact their Cisco support team for
    assistance in upgrading to a supported version of Cisco ASA
    Software.

    Note: The affected implementation of the Cisco Clientless VPN
    solution was introduced with the release of Cisco ASA Software
    version 7.1.  This issue does not affect devices running Cisco
    PIX Software.

Administrators may determine whether the Cisco Clientless VPN solution
is enabled on their devices by issuing the "show running-config webvpn"
command. The following example shows the response when the Cisco
Clientless VPN solution is enabled:

    ciscoasa# show running-config webvpn
    webvpn
     enable outside

End user systems running Microsoft Windows may be affected if they
have used the Cisco Clientless VPN feature on an affected device from
a browser that supports ActiveX technology.  Devices that contain the
cscopf.ocx ActiveX control registered with a class ID (CLSID) of
{B8E73359-3422-4384-8D27-4EA1B4C01232} are affected.  The affected
controls are marked both Safe for Scripting (SFS) and Safe for
Initialization (SFI), which may present additional attack vectors
when a system has registered and cached the affected control.

Products Confirmed Not Vulnerable
+--------------------------------

  * Cisco Firewall Service Modules are not affected by this
    vulnerability
  * Cisco Adaptive Security Appliance Services Modules are not
    affected by this vulnerability
  * Cisco IOS Software-based devices that use the Cisco Clientless
    VPN solution (WebVPN) are not affected by this vulnerability

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

Details
=======

Cisco Adaptive Security Appliances (ASA) contain a feature known as
the Cisco Clientless VPN solution.  The Cisco Clientless VPN feature
allows users to use a web browser to create an SSL VPN tunnel from an
endpoint device to a Cisco ASA device.  When connected, the ASA
pushes several ActiveX and Java applications to the endpoint device
to allow a number of features to operate.

When a browser that supports Microsoft ActiveX technology is used to
create the Clientless VPN tunnel, the Cisco Port Forwarder ActiveX
control may be sent to the endpoint system on which the browser is
running.  This control contains an exploitable buffer overflow
vulnerability that could allow an unauthenticated, remote attacker
who can convince a user to visit a malicious website to execute
attacker-controlled arbitrary code on the endpoint device.  The
attacker-supplied code would be executed with the privileges of the
user who invoked the browser used to visit the attacker-controlled
website.  If the user has administrative privileges, a complete
compromise may occur.

Upgrading a Cisco ASA device to a version of software that contains
the fixed control will not remediate the issue on endpoint systems
that have downloaded the affected control.  Affected endpoint systems
will need to disable the control via one of the methods suggested in
the "Workarounds" section of this document.  Endpoint systems may
also connect to a Cisco ASA device that is running a version of
software that contains the fixed control via the Cisco Clientless VPN
solution to update the control to an unaffected version.

When loaded on an endpoint system, the affected control has a binary
name of cscopf.ocx and is registered on a system with a CLSID of
{B8E73359-3422-4384-8D27-4EA1B4C01232}.  Fixed versions of the
cscopf.ocx control are registered with CLSID
{C861B75F-EE32-4aa4-B610-281AF26A8D1C}.

Cisco is requesting that Microsoft set a global kill bit for this
control in a future Microsoft kill-bit update. After this update
occurs, the affected control will stop operating on all affected
endpoint systems that load the Microsoft-provided update.

This advisory addresses the vulnerability in the Cisco Port Forwarder
ActiveX control provided by Cisco ASA when the Cisco Clientless VPN
feature is used. This issue is documented in Cisco bug ID CSCtr00165
and has been assigned Common Vulnerabilities and Exposures (CVE) ID
CVE-2012-0358.

Vulnerability Scoring Details
=============================

Cisco has scored the vulnerability in this advisory based on the
Common Vulnerability Scoring System (CVSS). The CVSS scoring in this
security advisory is in accordance with CVSS version 2.0.

CVSS is a standards-based scoring method that conveys vulnerability
severity and helps organizations determine the urgency and priority
of a response.

Cisco has provided a base and temporal score. Customers can also
compute environmental scores that help determine the impact of the
vulnerability in their own networks.

Cisco has provided additional information regarding CVSS at the
following link:

http://www.cisco.com/web/about/security/intelligence/cvss-qandas.html

Cisco has also provided a CVSS calculator to compute the
environmental impact for individual networks at the following link:

http://intellishield.cisco.com/security/alertmanager/cvss

* CSCtr00165 ("Cisco Clientless VPN Port Forwarder ActiveX Control
Remote Code Execution Vulnerability")

CVSS Base Score - 9.3
    Access Vector -            Network
    Access Complexity -        Medium
    Authentication -           None
    Confidentiality Impact -   Complete
    Integrity Impact -         Complete
    Availability Impact -      Complete

CVSS Temporal Score - 7.7
    Exploitability -           Functional
    Remediation Level -        Official-Fix
    Report Confidence -        Confirmed

Impact
======

Successful exploitation of the vulnerability may allow a remote,
unauthenticated attacker to execute arbitrary code on the affected
end-user system with the privileges of the user who invoked the web
browser.  If the user has administrative privileges, code execution
may result in a complete compromise of the affected system.

Software Versions and Fixes
===========================

When considering software upgrades, customers are advised to
consult the Cisco Security Advisories and Responses archive at
http://www.cisco.com/go/psirt and review subsequent advisories to
determine exposure and a complete upgrade solution.

In all cases, customers should ensure that the devices to be upgraded
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.

    +---------------------------------------------------------------+
    |Affected      | First Fixed     | Recommended Release          |
    |Version       |Release          |                              |
    |--------------+-----------------+------------------------------|
    |Cisco ASA 7.0 |Not Vulnerable   |Migrate to 7.2 or later       |
    |--------------+-----------------+------------------------------|
    |Cisco ASA 7.1 |Vulnerable       |Vulnerable; Migrate to 7.2 or |
    |              |                 |later                         |
    |--------------+-----------------+------------------------------|
    |Cisco ASA 7.2 | 7.2(5.6)        |7.2(5.7)                      |
    |--------------+-----------------+------------------------------|
    |Cisco ASA 8.0 |8.0(5.26)        |Migrate to 8.2(5.26) or later |
    |--------------+-----------------+------------------------------|
    |Cisco ASA 8.1 | 8.1(2.53)       |Migrate to 8.2(5.26) or later |
    |--------------+-----------------+------------------------------|
    |Cisco ASA 8.2 | 8.2(5.18)       |8.2(5.26)                     |
    |--------------+-----------------+------------------------------|
    |Cisco ASA 8.3 | 8.3(2.28)       |Migrate to 8.4(3.8) or later  |
    |--------------+-----------------+------------------------------|
    |Cisco ASA 8.4 |8.4(2.16)        |8.4(3.8)                      |
    |--------------+-----------------+------------------------------|
    |Cisco ASA 8.5 |Not Vulnerable   |8.5(1.7)                      |
    |--------------+-----------------+------------------------------|
    |Cisco ASA 8.6 |8.6(1.1)         |8.6(1.1)                      |
    +---------------------------------------------------------------+

    Note: Cisco ASA Software version 7.0 and 7.1 have reached end of
    software maintenance. Customers who are using Cisco ASA Software
    version 7.0 or 7.1 should contact their Cisco support team for
    assistance in upgrading to a supported version of Cisco ASA
    Software.

    Note: The recommended releases contain the fixes for all
    vulnerabilities for all the advisories published in the
    publication. Cisco recommends upgrading to a release that is
    equal to or later than these recommended releases.

    Note: Upgrading a Cisco ASA device to a version of software that
    contains the fixed version of the Cisco Port Forwarder ActiveX
    control does not remove the vulnerability on affected endpoint
    systems.  Affected endpoint systems will need to download the
    fixed version by connecting to a Cisco ASA device that is running
    fixed software via the Cisco Clientless Web solution or disable
    the affected control via one of the methods mentioned in the
    "Workarounds" section of this document.

Workarounds
===========

End users or administrators may mitigate Internet Explorer as an
attack vector by setting the kill bit for the affected ActiveX
control.  This can be achieved by modifying the registry either
directly on the affected machine or via an Active Directory Group
Policy. 

Warning: Incorrectly modifying the system registry of a Microsoft
Windows-based device may cause serious problems.  Neither Cisco nor
Microsoft can guarantee that you can resolve problems that may result
from improper registry modification from either applying the registry
changes via a .reg file or by using the Registry Editor incorrectly. 
Modify the registry of your system at your own risk.

To set the kill bit for the CLSID with a value of
{B8E73359-3422-4384-8D27-4EA1B4C01232}, paste the following text in a
text editor such as Notepad.  Save the file using the .reg filename
extension.

    Windows Registry Editor Version 5.00
    [HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\ActiveX Compatibility\{B8E73359-3422-4384-8D27-4EA1B4C01232}]
    "Compatibility Flags"=dword:04000400

    [HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Internet Explorer\ActiveX Compatibility\{B8E73359-3422-4384-8D27-4EA1B4C01232}]
    "Compatibility Flags"=dword:04000400

End users can apply this .reg file to individual systems by
double-clicking the file.  Administrators can also apply the registry
change across domains by using Group Policy.  You can find more
information about using Group Policy in the following Microsoft
TechNet article: Group Policy Collection

When the registry change has been applied, Microsoft Internet
Explorer must be restarted for the changes to take effect.  Once the
kill bit has been set, the affected control will no longer be
accessible by the Cisco Clientless VPN system or a malicious web page
when accessed by Internet Explorer.  This change may impact some
clientless installations that use the Cisco Port Forwarder ActiveX
control. One common component that may stop operating is the ActiveX
RDP plug-in.

Mitigations that can be deployed on Cisco devices in a network are
available in the Cisco Applied Intelligence companion document for
this advisory:

http://tools.cisco.com/security/center/content/CiscoAppliedMitigationBulletin/cisco-amb-20120314-asaclient

Obtaining Fixed Software
========================

Cisco has released free software updates that address the
vulnerability described in this advisory. Prior to deploying
software, customers are advised to consult their maintenance
providers or check the software for feature set compatibility and
known issues that are specific to their environments.

Customers may only install and expect support for feature
sets they have purchased. By installing, downloading,
accessing, or otherwise using such software upgrades, customers
agree to follow the terms of the Cisco software license at
http://www.cisco.com/en/US/docs/general/warranty/English/EU1KEN_.html,
or as set forth at
http://www.cisco.com/public/sw-center/sw-usingswc.shtml.

Do not contact psirt at cisco.com or security-alert at cisco.com for
software upgrades.

Customers with Service Contracts
+-------------------------------

Customers with contracts should obtain upgraded software through their
regular update channels. For most customers, upgrades should be obtained
through the Software Center on Cisco.com at http://www.cisco.com.

Customers Using Third-Party Support Organizations
+------------------------------------------------

Customers with Cisco products that are provided or maintained through
prior or existing agreements with third-party support organizations,
such as Cisco Partners, authorized resellers, or service providers,
should contact that organization for assistance with the appropriate
course of action.

The effectiveness of any workaround or fix depends on specific
customer situations, such as product mix, network topology, traffic
behavior, and organizational mission. Because of the variety of
affected products and releases, customers should consult their
service providers or support organizations to ensure that any applied
workaround or fix is the most appropriate in the intended network
before it is deployed.

Customers Without Service Contracts
+----------------------------------

Customers who purchase directly from Cisco but do not hold a Cisco
service contract and customers who make purchases through third-party
vendors but are unsuccessful in obtaining fixed software through
their point of sale should obtain upgrades by contacting the Cisco
Technical Assistance Center (TAC):

  * +1 800 553 2447 (toll free from within North America)
  * +1 408 526 7209 (toll call from anywhere in the world)
  * e-mail: tac at cisco.com

Customers should have the product serial number available and be
prepared to provide the URL of this advisory as evidence of
entitlement to a free upgrade. Customers without service contracts
should request free upgrades through the TAC.

Refer to Cisco Worldwide Contacts at
http://www.cisco.com/en/US/support/tsd_cisco_worldwide_contacts.html
for additional TAC contact information, including localized telephone
numbers, instructions, and e-mail addresses for support in various
languages.

Exploitation and Public Announcements
=====================================

The Cisco Product Security Incident Response Team (PSIRT) is not
aware of any public announcements or malicious use of the
vulnerability that is described in this advisory.

This vulnerability was reported to Cisco by Will Dormann of the CERT/CC.

Status of This Notice: Final
============================

THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY
KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE
INFORMATION ON THE DOCUMENT OR MATERIALS LINKED FROM THE DOCUMENT IS
AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS
DOCUMENT AT ANY TIME.

A stand-alone copy or Paraphrase of the text of this document that
omits the distribution URL in the following section is an
uncontrolled copy, and may lack important information or contain
factual errors.

Distribution
============

This advisory is posted on Cisco Security Intelligence Operations at
the following link:

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20120314-asaclient

Additionally, a text version of this advisory is clear signed with
the Cisco PSIRT PGP key and circulated among the following e-mail
addresses:

  * cust-security-announce at cisco.com
  * first-bulletins at lists.first.org
  * bugtraq at securityfocus.com
  * vulnwatch at vulnwatch.org
  * cisco at spot.colorado.edu
  * cisco-nsp at puck.nether.net
  * full-disclosure at lists.grok.org.uk

Future updates of this advisory, if any, will reside on Cisco.com but
may not be announced on mailing lists. Users can monitor this
advisory's URL for any updates.

Revision History
================

+------------------------------------------------------------+
| Revision 1.0   | 2012-Mar-14  | Initial public release.    |
+------------------------------------------------------------+

Cisco Security Procedures
=========================

Complete information about reporting security vulnerabilities in Cisco
products, obtaining assistance with security incidents, and registering
to receive security information from Cisco is available on Cisco.com at
http://www.cisco.com/en/US/products/products_security_vulnerability_policy.html.
This web page includes instructions for press inquiries
regarding Cisco Security Advisories. All Cisco Security Advisories are
available at http://www.cisco.com/go/psirt.

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