[KIS-2014-08] OpenCart <= 1.5.6.4 (cart.php) PHP Object Injection Vulnerability

[Egidio Romano <research@xxxxxxxxxxxxxxxxxxx>]

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OpenCart <= 1.5.6.4 (cart.php) PHP Object Injection Vulnerability
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[-] Software Link:

http://www.opencart.com/


[-] Affected Versions:

Version 1.5.6.4 and prior versions.


[-] Vulnerability Description:

The vulnerable code is located in the "Cart::getProducts()" method defined in 
/system/library/cart.php:

23.             foreach ($this->session->data['cart'] as $key => $quantity) {
24.                     $product = explode(':', $key);
25.                     $product_id = $product[0];
26.                     $stock = true;
27.     
28.                     // Options
29.                     if (!empty($product[1])) {
30.                             $options = 
unserialize(base64_decode($product[1]));
31.                     } else {
32.                             $options = array();
33.                     }

The vulnerability exists because this method uses the "unserialize()" function 
with the key values of the
array stored into the "data['cart']" session variable without a proper 
validation.  Such values might be
manipulated by an unauthenticated attacker via the $_POST['quantity'] parameter 
during an "update" request.
This can be exploited to inject arbitrary PHP objects into the application 
scope, and could allow an attacker
to conduct Server-Side Request Forgery (SSRF) attacks by abusing the destructor 
method of the "DBMySQLi"
class and possibly other attacks leveraging magic methods of classes defined in 
third-party extensions.

NOTE: if OpenCart is running on PHP before version 5.3.23 or 5.4.13 this 
vulnerability
could also be exploited to carry out XML External Entity (XXE) attacks, which 
in turn
might allow arbitrary command execution if the PHP "expect" extension is 
installed.


[-] Solution:

Update to version 1.5.6.5 when will be released or apply this patch: 
http://git.io/F3dGoA


[-] Disclosure Timeline:

[02/06/2014] - First attempt to contact the vendor
[04/06/2014] - Issue reported to http://git.io/uOsKfA
[06/06/2014] - CVE number requested
[06/06/2014] - CVE number assigned
[25/06/2014] - Vendor contacted again asking when will be released a fixed 
version
[25/06/2014] - Vendor replied there's no need to alert its users because the 
vulnerability is very weak
[14/07/2014] - Public disclosure


[-] CVE Reference:

The Common Vulnerabilities and Exposures project (cve.mitre.org)
has assigned the name CVE-2014-3990 to this vulnerability.


[-] Credits:

Vulnerability discovered by Egidio Romano.


[-] Original Advisory:

http://karmainsecurity.com/KIS-2014-08