Red Hat Certificate System (RHCS) 7.3 and 8 and Dogtag Certificate System allow remote authenticated users to generate an arbitrary number of certificates by replaying a single SCEP one-time PIN.
https://rhn.redhat.com/errata/RHSA-2010-0838.html
https://rhn.redhat.com/errata/RHSA-2010-0837.html
https://fedorahosted.org/pki/changeset/1246
https://bugzilla.redhat.com/show_bug.cgi?id=648883