With the emergence of 5G networks and their large scale applications such as IoT and autonomous vehicles, telecom operators are increasingly offloading the computation closer to customers (i.e., on the edge). Such edge-core environments usually involve multiple Kubernetes clusters potentially owned by different providers. Confidentiality and privacy concerns could prevent those providers from sharing data freely with each other, which makes it challenging to perform common security tasks such as security verification and attack/anomaly detection across different clusters. In this work, we propose CCSM, a solution for building cross-cluster security models to enable various security analyses, while preserving confidentiality and privacy for each cluster. We design a six-step methodology to model both the cross-cluster communication and cross-cluster event dependency, and we apply those models to different security use cases. We implement our solution based on a 5G edge-core environment that involves multiple Kubernetes clusters, and our experi�mental results demonstrate its efficiency (e.g., less than 8 s of processing time for a model with 3,600 edges and nodes) and accuracy (e.g., more than 96% for cross-cluster event prediction)