Lack of authentication of servers, and thereby authenticity of records

Its latency, which enables insertion of records between the time when a record has expired and when it is refreshed

The fact that it is a simple, distributed, hierarchical database instead of a singular, relational one, thereby giving rise to the possibility of inconsistencies going undetected for a certain amount of time

The fact that addresses in e-mail can be spoofed without checking their validity in DNS, caused by the fact that DNS addresses are not digitally signed