The remoting module in Jenkins before 2.32 and LTS before 2.19.3 allows remote attackers to execute arbitrary code via a crafted serialized Java object, which triggers an LDAP query to a third-party server.
https://groups.google.com/forum/#!original/jenkinsci-advisories/-fc-w9tNEJE/GRvEzWoJBgAJ
https://groups.google.com/forum/#!original/jenkinsci-advisories/-fc-w9tNEJE/LZ7EOS0fBgAJ
https://www.exploit-db.com/exploits/44642/