Techniques for preventing sequence number leakage during user equipment authentication in a communication network are provided. For example, a method comprises obtaining a permanent identifier and an authentication sequence value that are unique to user equipment, concealing the permanent identifier and the authentication sequence value, and sending the concealed permanent identifier and the authentication sequence value in a registration message from the user equipment to a communication network. Then, advantageously, in response to receipt of an authentication failure message from the communication network, the user equipment can send a response message to the communication network containing a failure cause indication without a re-synchronization token.