As the connectivity of vehicles grows and becomes more intelligent, security threats are also increasing. In fact, hacking of vehicles such as Jeep Cherokee (2014), Mitsubishi Outlander (2016) and Tesla model S (2016 and 2017) has been reported. Currently, various intrusion detection solutions are emerging in order to defend the cyber-attacks of vehicles, but up to now, the response to detection has remained at the ex post countermeasure level. In this paper, we propose a mitigation mechanism to cope with an attack on a vehicular internal network. The proposed mechanism reconfigures ECUs and disables attack packets to mitigate damage to network intrusions.