sshd in OpenSSH before 7.3, when SHA256 or SHA512 are used for user password hashing, uses BLOWFISH hashing on a static password when the username does not exist, which allows remote attackers to enumerate users by leveraging the timing difference between responses when a large password is provided.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.922
EPSS Ranking 99.7%