Software Engineering Institute

Cisco AnyConnect is an SSL VPN solution that is commonly initiated through use of a web browser. When Internet Explorer is used, the AnyConnect VPN server provides an ActiveX control that downloads and installs the AnyConnect client software. One of the components provided by Cisco AnyConnect for use with Internet Explorer is an ActiveX control called the "CISCO Portforwarder Control." This ActiveX control is provided by the file ciscopf.ocx. The Cisco Portforwarder ActiveX control contains a buffer overflow in its initialization parameters. We have confirmed that version 1.0.1.8 of the Portforwarder control is vulnerable. Previous versions may also be affected.

By convincing a user to view a specially crafted HTML document (e.g., a web page or an HTML email message or attachment), an attacker may be able to execute arbitrary code.

Apply an update

This issue is addressed in Cisco Security Advisory cisco-sa-20120314-asaclient. Please note that updating a Cisco ASA device with the fixed software will not protect systems that have already downloaded the vulnerable control. Please also consider the following workarounds:

Disable the Cisco AnyConnect Portforwarder ActiveX control in Internet Explorer

The vulnerable Cisco AnyConnect Portforwarder ActiveX control can be disabled in Internet Explorer by setting the kill bit for the following CLSID:

{B8E73359-3422-4384-8D27-4EA1B4C01232}
More information about how to set the kill bit is available in Microsoft Support Document 240797. Alternatively, the following text can be saved as a .REG file and imported to set the kill bit for this control:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\ActiveX Compatibility\{B8E73359-3422-4384-8D27-4EA1B4C01232}]
"Compatibility Flags"=dword:00000400
[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Internet Explorer\ActiveX Compatibility\{B8E73359-3422-4384-8D27-4EA1B4C01232}]
"Compatibility Flags"=dword:00000400