Serialisation related security vulnerabilities have recently been reported for numerous Java applications. Since serialisation presents both soundness and precision challenges for static analysis, it can be difficult for analyses to precisely pinpoint serialisation vulnerabilities in a Java library. In this paper, we propose a hybrid approach that extends a static analysis with fuzzing to detect serialisation vulnerabilities. The novelty of our approach is in its use of a heap model to direct fuzzing for vulnerabilities in Java libraries. The advantage is that the analysis guides fuzzing to quickly and effectively produce results, which may also automatically validate static analysis reports.