SynopsisThe remote Debian host is missing a security-related update.
DescriptionEddie 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.
SolutionUpgrade the openssh packages.
For the stable distribution (jessie), this problem has been fixed in version 1:6.7p1-5+deb8u3.