This issue is not directly exploitable.This issue is mitigated by the fact that in order for it to be exploitable, a separate vulnerability must be present to allow an attacker to pass unsafe input to unserialize(). There are no such known exploits in Drupal core.
Drupal core contains a chain of methods that could be exploitable when an insecure deserialization vulnerability exists on the site. This so-called “gadget chain” presents no direct threat, but is a vector that can be used to achieve remote code execution or SQL injection if the application deserializes untrusted data due to another vulnerability.



