The growing density of cellular users is placing an unprecedented demand on radio spectrum. Cognitive cellular networks can alleviate spectrum demand through dynamic spectrum access. In order to be fully functional, cellular users not only need spectrum access but also require network access. However, a cellular carrier grants network access only to accredited users. In this paper, we focus on the problem of opportunistic network access for unaccredited users by spontaneous provisioning in the context of cognitive cellular networks. We achieve this for both single and group users by extending the traditional 3A security framework - authentication, authorization, and accounting - to a 5A security paradigm. This entails the addition of network access and user assertion. We design several simulations based on a proof-of-principle prototype to validate our approach against multiple traffic models. The results show our approach can deliver at least 13% improvement in user provisioning time compared to conventional schemes.