package com.govuln; import java.lang.reflect.Method; import java.util.Base64; public class HelloDefineClass { public static void main(String[] args) throws Exception { Method defineClass = ClassLoader.class.getDeclaredMethod("defineClass", String.class, byte[].class, int.class, int.class); defineClass.setAccessible(true); // source: bytecodes/Hello.java byte[] code = Base64.getDecoder().decode("yv66vgAAADQAHAoABgAOCQAPABAIABEKABIAEwcAFAcAFQEABjxpbml0PgEAAygpVgEABENvZGUBAA9MaW5lTnVtYmVyVGFibGUBAAg8Y2xpbml0PgEAClNvdXJjZUZpbGUBAApIZWxsby5qYXZhDAAHAAgHABYMABcAGAEAC0hlbGxvIFdvcmxkBwAZDAAaABsBAAVIZWxsbwEAEGphdmEvbGFuZy9PYmplY3QBABBqYXZhL2xhbmcvU3lzdGVtAQADb3V0AQAVTGphdmEvaW8vUHJpbnRTdHJlYW07AQATamF2YS9pby9QcmludFN0cmVhbQEAB3ByaW50bG4BABUoTGphdmEvbGFuZy9TdHJpbmc7KVYAIQAFAAYAAAAAAAIAAQAHAAgAAQAJAAAAHQABAAEAAAAFKrcAAbEAAAABAAoAAAAGAAEAAAACAAgACwAIAAEACQAAACUAAgAAAAAACbIAAhIDtgAEsQAAAAEACgAAAAoAAgAAAAQACAAFAAEADAAAAAIADQ=="); Class hello = (Class)defineClass.invoke(ClassLoader.getSystemClassLoader(), "Hello", code, 0, code.length); hello.newInstance(); } }