Infinite Token (or Token Cycling) vulnerability occurs when a refresh token is designed in a way that it never expires or can continuously issue new refresh tokens. This allows for indefinite authentication sessions, even in cases where a token is compromised.

Remediation

• Always enforce a finite lifetime for refresh tokens, ensuring they expire after a reasonable period.
• Implement a rotation mechanism where each refresh token is single-use and a new one is issued upon successful usage. Revoke the old token upon rotation.
• Use sliding expiration for refresh tokens, where the lifetime is extended only when valid tokens are used near expiration. Avoid indefinite extensions.
• * Ensure that logging out invalidates all active tokens, both access and refresh, across devices.
• Require users to re-authenticate periodically or for high-risk actions, reducing reliance on long-lived tokens.