Public Vulnerability Reports

Cisco AnyConnect VPN Client Arbitrary Program Execution Vulnerability

01.06.11

BACKGROUND

Cisco's AnyConnect VPN solution provides remote access to customers via the Web browser. This is accomplished through the use of a Java applet. The applet itself is provided by the server upon connecting. Cisco states that AnyConnect VPN supports all Adaptive Security Appliance (ASA) models. For more information, visit the following URL.

http://www.cisco.com/en/US/docs/security/vpn_client/anyconnect/anyconnect23/release/notes/anyconnect23rn.html

DESCRIPTION

Remote exploitation of a design error vulnerability within Cisco Systems Inc's AnyConnect VPN Java client allows attackers to execute arbitrary code with the privileges of the targeted user.

The Java applet is used to install the VPN client. Once it is instantiated, it will attempt to download two files from the site specified in the "url" property. As such, an attacker can craft a page such that the control will download an executable of their choosing.

One of the files will be executed upon the successful completion of the download. This allows an attacker to execute an arbitrary executable on the user's system.

This vulnerability is nearly identical to a previous iDefense disclosure. However, rather than exploiting the ActiveX control through JavaScript, this vulnerability exploits the JRE applet.

ANALYSIS

Exploitation allows attackers to execute arbitrary code in the context of the currently logged-on user. To exploit this vulnerability, a targeted user must load a malicious Web page created by an attacker. An attacker typically accomplishes this via social engineering or injecting content into compromised, trusted sites.

Additionally, in a default configuration, a targeted user must have this control already installed or must accept several warning prompts at the time that the attack is taking place. If the control is already installed, all an attacker has to do to exploit the vulnerability is embed a link to an executable which will be downloaded and executed.

DETECTION

Cisco AnyConnect VPN client versions prior to 2.3.185 for Windows, 2.5.3041 and 3.0.629 for Linux and Apple Mac OS X are vulnerable.

WORKAROUND

iDefense is currently unaware of any workarounds for this vulnerability.

VENDOR RESPONSE

Cisco has released an advisory which describes methods of updating the AnyConnect Secure Mobility Client. For more information, consult their advisory at the following URL.

http://www.cisco.com/en/US/products/products_security_advisory09186a00 80b80123.shtml

CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2011-2040 to this issue. This is a candidate for inclusion in the CVE list (http://cve.mitre.org/), which standardizes names for security problems.

DISCLOSURE TIMELINE

08/11/2010 Initial Vendor Notification
08/12/2010 Initial Vendor Reply
06/01/2011 Coordinated Public Disclosure

CREDIT

This vulnerability was reported to iDefense by Elazar Broad.

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LEGAL NOTICES

Copyright © 2011 Verisign, Inc.

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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.