c3p0 is a JDBC Connection pooling library. In versions prior to 0.14.0, c3p0 in combination with other libraries, can compose to a "sink" for deserialization gadgets. The JDBC spec's DataSource.getConnection() and ConnectionPoolDataSource.getPooledConnection() match the getXXX() form, so JavaBean libraries treat them as "properties" assumed safe while they actually call into JDBC drivers. Attackers can thus craft malicious DataSource objects whose property lookups invoke vulnerable drivers, then smuggle them in serialized form to where an application deserializes and auto-resolves bean properties — triggering the attack. This requires a susceptible DataSource/ConnectionPoolDataSource and JDBC driver on the CLASSPATH, plus a carrier that auto-looks-up JavaBean properties on = deserialization, most commonly a collection paired with an Apache commons-beanutils Comparator that sorts by bean properties. c3p0 supplied that susceptible DataSource/ConnectionPoolDataSource, which was an essential component of the trigger. This issue has been fixed in version 0.14.0.