What is a common issue with Signature Verification of JWTs?

Mixing up algorithms can lead to significant issues in signature verification of JSON Web Tokens (JWTs). When a token is created, it is signed using a specific algorithm, and the recipient must use the same algorithm to verify the signature. If the algorithm specified in the JWT header does not match the algorithm used to sign the token, this mismatch prevents successful signature verification.

For example, if a token is signed using the HMAC algorithm but the verifier is set to use RSA for signature verification, the signature cannot be validated correctly. This can create security vulnerabilities, such as allowing unauthorized access if the system fails to correctly recognize that the signature is invalid. Ensuring that the algorithm used during signature creation is the same as the one used during verification is crucial for maintaining the integrity and security of the authentication process associated with JWTs.