Deserialization of untrusted data in the report-processing code of Puppet, as used by Puppet Server, in the affected releases, allows a client that holds any CA-signed agent certificate to execute arbitrary code on the Puppet Server as its service user by submitting a report containing a crafted rich-data type via PUT request. Where the certificate authority autosigns requests without strong verification, an unauthenticated network attacker can obtain such a certificate.