The disadvantages of JSON Web Tokens (JWT) include:
Size: JWTs can be larger than traditional session tokens because they contain claims and signature information. This can lead to increased bandwidth usage, especially for mobile applications where data usage is a concern.
Example: A JWT might be several hundred bytes, whereas a session ID could be just a few dozen bytes.
Security Risks: If a JWT is stolen, it can be used to impersonate the user until it expires. Unlike session tokens stored on the server, JWTs are stateless and do not expire on the server side.
Example: If an attacker gains access to a user's JWT, they can use it to access protected resources without needing the user's credentials.
Token Expiry: JWTs have expiration times, but once expired, they cannot be refreshed without the user re-authenticating. This can lead to a poor user experience if not handled properly.
Example: A user might be logged out unexpectedly if their JWT expires, requiring them to log back in.
Complexity in Revocation: Unlike session tokens, which can be easily revoked by invalidating the session on the server, JWTs cannot be revoked without changing the secret key or using a blacklist approach, which adds complexity.
Example: If a user's permissions change or they need to be logged out for security reasons, revoking a JWT requires additional mechanisms to ensure it is no longer valid.
Storage on Client-Side: JWTs are stored on the client side, which can be vulnerable to access by malicious scripts or attackers with access to the user's device.
Example: If a user's device is compromised, an attacker could potentially access and use the stored JWT.
For cloud-based applications, managing JWTs securely can be challenging. Services like Tencent Cloud offer solutions such as Tencent Cloud Security Token Service (STS), which provides secure token management features to help mitigate some of these disadvantages.