Frankencerts are specially crafted SSL certificates for testing certificate validation code in SSL/TLS implementations. The technique is described in detail in the 2014 IEEE Symposium on Security and Privacy (Oakland) paper - Using Frankencerts for Automated Adversarial Testing of Certificate Validation in SSL/TLS Implementations by Chad Brubaker, Suman Jana, Baishakhi Ray, Sarfraz Khurshid, and Vitaly Shmatikov.
more here....https://github.com/sumanj/frankencert
more here....https://github.com/sumanj/frankencert