Piwik <= 2.16.0 (saveLayout) PHP Object Injection Vulnerability

• Software Link:

https://piwik.org/

• Affected Versions:

Version 2.16.0 and prior versions.

• Vulnerability Description:

The vulnerability can be triggered through the saveLayout() method defined into the /plugins/Dashboard/Controller.php script:

    public function saveLayout()
    {
        $this->checkTokenInUrl();

        $layout      = Common::unsanitizeInputValue(Common::getRequestVar('layout'));
        $layout      = strip_tags($layout);
        $idDashboard = Common::getRequestVar('idDashboard', 1, 'int');
        $name        = Common::getRequestVar('name', '', 'string');

        if (Piwik::isUserIsAnonymous()) {
            $session = new SessionNamespace("Dashboard");
            $session->dashboardLayout = $layout;
            $session->setExpirationSeconds(1800);

User input passed by anonymous users through the “layout” request parameter is being stored into a session variable
at line 221, and this is possible by invoking an URL like this:

http://[piwik]/index.php?module=Dashboard&action=saveLayout&token_auth=anonymous&layout=[injection]%26%2365536;

Since Piwik is not using “utf8mb4″ collations for its database, this can be exploited in combination with a MySQL UTF8
truncation issue in order to corrupt the session array, allowing unauthenticated attackers to inject arbitrary PHP objects into
the application scope and carry out Server-Side Request Forgery (SSRF) attacks, delete arbitrary files, execute arbitrary PHP
code, and possibly other attacks. Successful exploitation of this vulnerability requires Piwik to use the database to store
session data (dbtable option) and the application running on PHP before version 5.4.45, 5.5.29, or 5.6.13.

• Solution:

Update to version 2.16.1 or later.

• Disclosure Timeline:

[08/02/2016] – Vendor notified
[09/02/2016] – Vendor replied not to be able to reproduce the issue
[11/02/2016] – Proof of concept tested on demo.piwik.org sent to the vendor
[11/02/2016] – Vendor response stating the issue will be fixed in 2.16.1 release
[17/02/2016] – Bug bounty received
[11/04/2016] – Version 2.16.1 released: http://piwik.org/changelog/piwik-2-16-1/
[16/06/2016] – CVE number requested
[07/11/2016] – Public disclosure

• CVE Reference:

The Common Vulnerabilities and Exposures project (cve.mitre.org)
has not assigned a CVE identifier for this vulnerability.

• Credits:

Vulnerability discovered by Egidio Romano.