A Wireless Sensor Network (WSN) consists of numerous resource-constrained sensor nodes. Due to the broadcast nature of the wireless medium, security becomes a primary concern, and overlapping coverage among sensor nodes often leads to redundancy in data observation. WSNs are typically deployed in hostile and untrusted environments, which can result in the presence of malicious nodes. Consequently, detecting malicious nodes and ensuring energy efficiency are critical challenges in WSNs. This paper proposes a Cuckoo Search Algorithm based on Fuzzy Logic (CSA-FL) for malicious node detection and energy-efficient routing using a Mobile Sink (MS). In this approach, the MS acts as a mobile agent that collects data from Cluster Heads (CHs). Determining an optimal mobility trajectory for the MS is crucial to achieving energy efficiency. The proposed scheme introduces a fuzzy logic system to select CHs based on Hyper Round (HR). Additionally, the Cuckoo Search Algorithm (CSA) is utilized to detect malicious nodes within the network. Experimental results demonstrate that the proposed methodology enhances both the energy efficiency and throughput of the WSN.