Authentication Bypass by Capture-replay

Capture-replay attacks are a prevalent network threat where an adversary eavesdrops on a valid communication session, saves the transmitted data (like login requests or session tokens), and later resends that identical or slightly modified data to the server. Because the replayed data appears legitimate, the system grants access without requiring the attacker to know the actual credentials or break any encryption. These attacks are a specific type of network injection that can be challenging to prevent without implementing proper cryptographic defenses. To mitigate this risk, developers need to ensure that each authentication request is unique and cannot be reused, typically by incorporating timestamps, nonces, or sequence numbers that the server can validate.