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Piwik <= 2.16.0 (saveLayout) PHP Object Injection Vulnerability
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[-] 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 in /plugins/Dashboard/Controller.php:

210.    public function saveLayout()
211.    {
212.        $this->checkTokenInUrl();
213.
214.        $layout      = 
Common::unsanitizeInputValue(Common::getRequestVar('layout'));
215.        $layout      = strip_tags($layout);
216.        $idDashboard = Common::getRequestVar('idDashboard', 1, 'int');
217.        $name        = Common::getRequestVar('name', '', 'string');
218.
219.        if (Piwik::isUserIsAnonymous()) {
220.            $session = new SessionNamespace("Dashboard");
221.            $session->dashboardLayout = $layout;
222.            $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.


[-] Original Advisory:

http://karmainsecurity.com/KIS-2016-13