Recent advances in inter-vehicle wireless communications allow for automated and coordinated vehicles' driving in platoon-based vehicular cyber-physical systems (PVCPS). This article presents a comprehensive low-latency cooperative security (LLCS) framework for secure and timely data dissemination in PVCPS. A new cooperative secret key agreement protocol is incorporated to produce secret keys for platooning vehicles based on their radio channel correlation. A new transmit rate adaptation mechanism is presented to minimize the end-to-end latency of the data dissemination in PVCPS. We also numerically test the confidentiality and timeliness of the LLCS framework in terms of key agreement probability and dissemination delay. It is believed that the LLCS framework is the demand of the time to enable secure and reliable autonomous driving for future PVCPS.