A flaw was found in MIT krb5 1.6 or later, an authenticated kadmin user with permission to add principals to an LDAP Kerberos database can circumvent a DN containership check by supplying both a "linkdn" and "containerdn" database argument, or by supplying a DN string which is a left extension of a container DN string but is not hierarchically within the container DN.

Reference: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=891869

Upstream patch: https://github.com/krb5/krb5/commit/e1caf6fb74981da62039846931ebdffed71309d1