Debian Linux Security Advisory 3626-1 - Eddie Harari reported that the OpenSSH SSH daemon allows user enumeration through timing differences when trying to authenticate users. When sshd tries to authenticate a non-existing user, it will pick up a fixed fake password structure with a hash based on the Blowfish algorithm. If real users passwords are hashed using SHA256/SHA512, then a remote attacker can take advantage of this flaw by sending large passwords, receiving shorter response times from the server for non-existing users. Continue reading...
