With technological advancements, vehicular ad hoc networks (VANETs) are poised to revolutionize road transportation, addressing issues like road accidents and traffic congestion. However, ensuring the security of VANETs is paramount, as unauthorized communications can lead to severe consequences, including accidents. Traditional security mechanisms based on the integer factorization problem and the discrete logarithm problem (DLP) are vulnerable to Shor’s algorithm on quantum computers. Ahmad and Jagatheswari proposed a post-quantum-secured LBA-PAKE protocol for VANETs using lattice-based hard problems. However, when we performed cryptanalysis on their protocol, we identified that it is vulnerable to denial-of-service and replay attacks. Moreover, it fails to achieve a robust login phase and mutual authentication. We propose a countermeasure for VANETs based on RLWE for anonymous authorized communication protocol to ensure secure and authorized communication. Our countermeasure ensures quantum safety, mitigates denial-of-service attacks, and supports mutual authentication. Furthermore, our evaluation demonstrates that the proposed countermeasure is computationally more efficient than the LBA-PAKE protocol for VANETs.