Telekom Security security.telekom.com Advisory: Kaltura - Remote Code Execution and Cross-Site Scripting Release Date: 2017/09/12 Author: Robin Verton (robin.verton@telekom.de) CVE: CVE-2017-14141, CVE-2017-14142, CVE-2017-14143 Application: Kaltura <= 13.1.0 Risk: Critical Vendor Status: Kaltura 13.2.0 was released to fix this vulnerabilities. Overview: Quote from Wikipedia: "Kaltura is a New York-based software company founded in 2006. Kaltura states that its mission is to power any video experience. Kaltura operates in four major markets for video based solutions: Cloud TV (AKA OTT TV) for operators and media companies, OVP (Online Video Platform) offered mostly to media companies and brands looking to distribute content or monetize it, EdVP (Education Video Platform) offered to educational institutions who are increasingly relying on video as for teaching and learning, and EVP (Enterprise Video Platform) offered to enterprises who use video for collaboration, communications and marketing." Kaltura is installed on a lot of high profiles website like banking websites, universities, manufacturers, multimedia corporations etc. Multiple vulnerabilities were identified in the current release of the Kaltura Video platform. It was discovered that Kaltura passes unfiltered user input to unserialize(), leading to the execution of PHP code. One of this vulnerabilities can also be triggered unauthenticated. Several other Cross-Site Scripting vulnerabilities were found. Details: 1) Unauthenticated Remote Code Execution through unserialize() from cookie data Because of a hardcoded cookie secret, the cookie signature validation can be bypassed and malicious user input can be passed via the 'userzone' cookie to the unserialize() function: abstract class kalturaAction extends sfAction { private $cookieSecret = 'y3tAno3therS$cr3T'; // [...] protected function getUserzoneCookie() { $cookie = $this->getContext()->getRequest()->getCookie('userzone'); $length = strlen($cookie); if ($length <= 0) return null; $serialized_data = substr($cookie, 0, $length - 32); $hash_signiture = substr($cookie, $length - 32); // check the signiture if (md5($serialized_data . $this->cookieSecret) != $hash_signiture) return null; $userzone_data = unserialize(base64_decode($serialized_data)); To pass this validation the base64 encoded serialized object has to be hashed and this hash appended to the encoded data. A Zend Framework POP chain [1] can then be used to execute PHP code when unserializing. When using PHP7 a different chain has to be used because the e-modifier for preg_replace is not available anymore. To execute the getUserzoneCookie() function the getAllEntriesAction has to be called with a valid entry ID. This ID can be obtained from any public video object which is embedded and typically begins with '0_'. 2) Authenticated Remote Code Execution through unserialize() in the admin panel The admin panel provides a few 'Developer System Helper' functions to encode/decode user supplied data. The 'wiki_decode' function will take user input and pass it nearly untouched to unserialize(): // slightly formatted for better readability if ( $algo == "wiki_encode" ) { $res = str_replace( array ( "|" , "/") , array ("|01" , "|02"), base64_encode(serialize($str)) ); } By passing a base64 encoded malicious serialized object, PHP code can be executed. 3) Multiple Cross-Site Scripting vulnerabilities under the API path A few cross-site scripting vulnerabilities were found earlier this year and fixed [2]. However, this fix was insufficient because PHPs strip_tags() function only strips tags and is not adequate to secure against XSS vulnerabilities. There are a few places where this can be exploited to inject javascript code: // server/admin_console/web/tools/bigRedButton.php, line 8 $partnerId = strip_tags($_GET['partnerId']); // [...] <script> var partnerId = <?php echo $partnerId; ?>; As can be seen above no tags need to be inserted here to execute javascript code. A simple partnerId=alert(1) will be executed in this scenario. This also affects a few other files. server/admin_console/web/tools/bigRedButton.php - $_GET['partnerId'] - $_GET['playerVersion'] server/admin_console/web/tools/bigRedButtonPtsPoc.php - $_GET['partnerId'] - $_GET['playerVersion'] - $_GET['secret'] - $_GET['entryId'] - $_GET['adminUiConfId'] - $_GET['uiConfId'] server/admin_console/web/tools/AkamaiBroadcaster.php - $_GET['streamUsername'] - $_GET['streamPassword'] - $_GET['streamRemoteId'] - $_GET['streamRemoteBackupId'] - $_GET['entryId'] server/admin_console/web/tools/XmlJWPlayer.php - $_GET['entryId'] server/alpha/web/lib/bigRedButtonPtsPocHlsjs.php - $_GET['partnerId'] - $_GET['playerVersion'] Additional notes: The already published Server Side Request Forgery attack [3] was not fixed properly, because only an additional check for the http(s) protocol was added. This still allows to talk to some backend services (like the memcached) or other machines. There is a whitelist in place to make this more secure, but I could not find a way how to set this up. This is likely responsible for a lot of insecure default installations of Kaltura in the wild. References: [1]: https://www.owasp.org/images/9/9e/Utilizing-Code-Reuse-Or-Return-Oriented-Programming-In-PHP-Application-Exploits.pdf [2]: https://github.com/kaltura/server/pull/5304/files [3]: http://www.security-assessment.com/files/documents/advisory/Kaltura-Multiple-Vulns.pdf Recommendation: It is recommended to upgrade to the latest version of Kaltura. Disclosure Timeline: 16. August 2017 - Notified vendor 22. August 2017 - Remote Command Execution vulnerabilities fixed 05. September 2017 - Cross-Site scripting vulnerabilities fixed 11. September 2017 - Kaltura 13.2.0 released 12. September 2017 - Released advisory About Telekom Security: Telekom Security is the security provider for Deutsche Telekom and Deutsche Telekom customers. https://security.telekom.com https://telekomsecurity.github.io http://www.sicherheitstacho.eu