5G networks tend to be multi-layered, multi-party and multi-tenant to satisfy the increasing and varying user demand. Network slicing is an efficient solution to share the physical network between different and independent virtual networks called slices. While many research works focused on the slice resource allocation, called slice embedding, little attention was paid to the security aspects. In this paper, we deal with security-aware 5G slice embedding. This consists in satisfying the slice request while meeting its security needs. In a first step, we model the common security needs and best practices for 5G slices. This is used to design a security-aware slice request. Second, we devise a slice embedding algorithm that respects the security constraints. Third, we analyse the scalability of making slice embedding security-aware, in terms of acceptance rate, cost to revenue ratio, execution time and physical resource utilization.