The present disclosure relates to a pre-5th-Generation (5G) or 5G communication system to be provided for supporting higher data rates Beyond 4th-Generation (4G) communication system such as Long Term Evolution (LTE). Methods, network entities, and systems for mitigating Denial of Service (DoS) attack in a wireless network (e.g., access network (AN), core network (CN)). Embodiments herein disclose methods and systems for mitigating Denial of Service (DOS) attacks in wireless networks, by performing admission control by verifying a User Equipment's (UE's) registration request via a Closed Access Group (CAG) cell without performing a primary authentication. Embodiments herein disclose methods and system for verifying permissions of the UE to access a CAG cell based on the UE's Subscription identifier, before performing the primary authentication. Methods and systems for mitigating Denial of Service (DoS) attack in a wireless network. A method for mitigating Denial of Service (DOS) attacks in wireless networks includes requesting a public land mobile network (PLMN) for accessing a non-public network (NPN) through a Closed Access Group (CAG) cell, verifying the permissions of a user equipment (UE) to access the requested NPN through the CAG cell, and performing a primary authentication.