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SEC Consult SA-20140716-1 :: Remote Code Execution via CSRF in OpenVPN Access Server "Desktop Client"
From: SEC Consult Vulnerability Lab <research () sec-consult com>
Date: Wed, 16 Jul 2014 14:11:19 +0300

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SEC Consult Vulnerability Lab Security Advisory < 20140716-1 >
=======================================================================
              title: Remote Code Execution via CSRF
            product: OpenVPN Access Server "Desktop Client"
 vulnerable version: all
      fixed version: not available
             impact: critical
           homepage: http://www.openvpn.net
              found: 2014-05-12
                 by: Stefan Viehböck
                     SEC Consult Vulnerability Lab
                     https://www.sec-consult.com
=======================================================================

Vendor description:
- -------------------
OpenVPN Technologies is a privately held company based in the Pleasanton,
California, integrating a suite of leading-edge networking and software
technologies.

Source: http://openvpn.net/index.php/about-menu/about-us.html

Business recommendation:
- ------------------------
Remote attackers can execute arbitrary code and execute other attacks on
computers with the OpenVPN Access Server "Desktop Client" installed. Affected
users should upgrade immediately to the OpenVPN Connect client.

Taken from OpenVPNs advisory:
"This advisory only applies to the OpenVPN Access Server "Desktop Client" app
for Windows, and does not affect OpenVPN Connect, Private Tunnel, or community
builds of OpenVPN for Windows."


Vulnerability overview/description:
- -----------------------------------
The OpenVPN Access Server "Desktop Client" consists of two parts, a Windows
service that offers an XML-RPC API via a webserver on localhost and a GUI
component that connects to this API.

The XML-RPC API is vulnerable to Cross-Site Request Forgery (CSRF). Using the
API commands an attacker can:
- - unmask a victim (e.g. by disconnecting an established VPN connection)
- - perform MITM attacks (by connecting the victim to an "evil" VPN server)
- - execute arbitrary code with SYSTEM privileges (by adding a VPN profile that
  executes code)


Proof of concept:
- -----------------
Detailed proof of concept exploits have been removed for this vulnerability.

A video demonstrating this issue has been released by SEC Consult:
https://www.youtube.com/watch?v=qhgysgfvQh8


Vulnerable / tested versions:
- -----------------------------
The vulnerabilities have been verified to exist in OpenVPN Access Server
"Desktop Client" version 1.5.6, which was the most recent version at the time
of discovery.
All other versions of the product are affected as well.


Vendor contact timeline:
- ------------------------
2014-05-12: Opening ticket at https://openvpn.net and attaching exploit and
            video.
2014-05-15: Vendor requests info about tested versions.
2014-05-15: Clarifying that tested version was obtained via
            http://swupdate.openvpn.net/downloads/openvpn-client.msi
2014-05-20: Vendor requests info about PrivateTunnel client (mentioned in
            initial advisory) and provides link to version with implemented
                        CSRF mitigations.
2014-05-21: Clarifying that PrivateTunnel might be affected and patch
            validation is not covered.
            [back and forth regarding whether PrivateTunnel is affected]
2014-07-01: Vendor announces that users should upgrade to OpenVPN Connect
            client.
2014-07-16: SEC Consult releases coordinated security advisory.


Solution:
- ---------
Upgrade to the OpenVPN Connect client.

More information can be found at:
http://openvpn.net/index.php/access-server/security-advisories.html


Workaround:
- -----------
No workaround available.


Advisory URL:
- -------------
https://www.sec-consult.com/en/Vulnerability-Lab/Advisories.htm


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
SEC Consult Vulnerability Lab

SEC Consult
Vienna - Bangkok - Frankfurt/Main - Montreal - Singapore - Vilnius

Headquarter:
Mooslackengasse 17, 1190 Vienna, Austria
Phone:   +43 1 8903043 0
Fax:     +43 1 8903043 15

Mail: research at sec-consult dot com
Web: https://www.sec-consult.com
Blog: http://blog.sec-consult.com
Twitter: https://twitter.com/sec_consult

Interested in working with the experts of SEC Consult?
Write to career () sec-consult com

EOF Stefan Viehböck / @2014
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