CDI specification does not allow proxying a class with non-private final methods. The java.util.Hashtable class has a non-private final method added to the class in later versions of Java, so a CDI application that previously worked may break when updating the Java level.
This issue was logged in CDI-527.
OpenWebBeans fixed this via the jira (https://issues.apache.org/jira/browse/OWB-616).
Can Weld fix this in the 2.3 or 2.2 trunk?