Downgrade attack

A downgrade attack is a form of attack on a computer system or communications protocol that makes it abandon a high-quality mode of operation in favor of an old, lower-quality mode of operation that is there for backward compatibility with older systems.

Downgrade attacks are often implemented as part of a man-in-the-middle attack, and may be used as a way of enabling a cryptographic attack that might not be possible otherwise. Downgrade attacks have been a consistent problem with the SSL/TLS family of protocols; examples of such attacks include the POODLE attack.

Removing backward compatibility is often the only way to prevent downgrade attacks.