A Polymorphic Typing issue was discovered in FasterXML jackson-databind 2.x before 2.9.9. When Default Typing is enabled (either globally or for a specific property) for an externally exposed JSON endpoint, the service has the mysql-connector-java jar (8.0.14 or earlier) in the classpath, and an attacker can host a crafted MySQL server reachable by the victim, an attacker can send a crafted JSON message that allows them to read arbitrary local files on the server. This occurs because of missing com.mysql.cj.jdbc.admin.MiniAdmin validation.