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.

c3p0, a JDBC Connection pooling library, is vulnerable to attack via maliciously crafted Java-serialized objects and `javax.naming.Reference` instances. Several c3p0 `ConnectionPoolDataSource` implementations have a property called `userOverridesAsString` which conceptually represents a `Map<String,Map<String,String>>`. Prior to v0.12.0, that property was maintained as a hex-encoded serialized object. Any attacker able to reset this property, on an existing `ConnectionPoolDataSource` or via maliciously crafted serialized objects or `javax.naming.Reference` instances could be tailored execute unexpected code on the application's `CLASSPATH`. The danger of this vulnerability was strongly magnified by vulnerabilities in c3p0's main dependency, mchange-commons-java. This library includes code that mirrors early implementations of JNDI functionality, including ungated support for remote `factoryClassLocation` values. Attackers could set c3p0's `userOverridesAsString` hex-encoded serialized objects that include objects "indirectly serialized" via JNDI references. Deserialization of those objects and dereferencing of the embedded `javax.naming.Reference` objects could provoke download and execution of malicious code from a remote `factoryClassLocation`. Although hazard presented by c3p0's vulnerabilites are exarcerbated by vulnerabilities in mchange-commons-java, use of Java-serialized-object hex as the format for a writable Java-Bean property, of objects that may be exposed across JNDI interfaces, represents a serious independent fragility. The `userOverridesAsString` property of c3p0 `ConnectionPoolDataSource` classes has been reimplemented to use a safe CSV-based format, rather than rely upon potentially dangerous Java object deserialization. c3p0-0.12.0+ and above depend upon mchange-commons-java 0.4.0+, which gates support for remote `factoryClassLocation` values by configuration parameters that default to restrictive values. c3p0 additionally enforces the new mchange-commons-java `com.mchange.v2.naming.nameGuardClassName` to prevent injection of unexpected, potentially remote JNDI names. There is no supported workaround for versions of c3p0 prior to 0.12.0.

c3p0 version < 0.9.5.4 may be exploited by a billion laughs attack when loading XML configuration due to missing protections against recursive entity expansion when loading configuration.

c3p0 0.9.5.2 allows XXE in extractXmlConfigFromInputStream in com/mchange/v2/c3p0/cfg/C3P0ConfigXmlUtils.java during initialization.