lib/puppet/ssl/certificate_authority.rb
in Puppet before 2.6.17 and 2.7.x before 2.7.18, and Puppet Enterprise before 2.5.2, does not properly restrict the characters in the Common Name field of a Certificate Signing Request (CSR), which makes it easier for user-assisted remote attackers to trick administrators into signing a crafted agent certificate via ANSI control sequences.