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 Viehbck 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 Viehbck / @2014