lib/puppet/network/authstore.rb in Puppet before 2.7.18, and Puppet Enterprise before 2.5.2, supports use of IP addresses in certnames without warning of potential risks, which might allow remote attackers to spoof an agent by acquiring a previously used IP address.
https://github.com/advisories/GHSA-vxf6-w9mp-95hm
https://github.com/puppetlabs/puppet/commit/ab9150baa1b738467a33b01df1d90e076253fbbd
https://euvd.enisa.europa.eu/vulnerability/EUVD-2017-0315