  In recent years, vehicles became able to establish connections with other
vehicles and infrastructure units that are located in the roadside. In the near
future, the vehicular network will be expanded to include the communication
between vehicles and any smart devices in the roadside which is called
Vehicle-to-Everything (V2X) communication. The vehicular network causes many
challenges due to heterogeneous nodes, various speeds and intermittent
connection, where traditional security methods are not always efficacious. As a
result, an extensive variety of research works has been done on optimizing
security solutions whilst considering network requirements. In this paper, we
present a comprehensive survey and taxonomy of the existing security solutions
for V2X communication technology. Then, we provide discussions and comparisons
with regard to some pertinent criteria. Also, we present a threat analysis for
V2X enabling technologies. Finally, we point out the research challenges and
some future directions.
