LR-WPANs mainly target low data rate and short range applications. Packet delivery in such networks is achieved through routing and packet forwarding. So we should provide security for both operations. In this paper, these two types of threats within the current LR-WPAN security architecture are identified and an efficient security framework (ESF) is presented. It protects both routing and data forwarding attacks. The framework involves detection of malicious nodes by the modified AODV routing and isolation of malicious nodes by using multi-signature based tickets. Through both analysis and simulation results, we demonstrate the effectiveness of our framework in detecting and isolating the misbehaving nodes.