Descriptionsshd 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.
SourceCVE (at NVD; CERT, LWN, oss-sec, fulldisc, bugtraq, EDB, Metasploit, Red Hat, Ubuntu, Gentoo, SuSE, Mageia, GitHub code/issues, web search, more)
ReferencesDLA-578-1, DSA-3626-1
NVD severitymedium (attack range: remote)
Debian Bugs831902

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
openssh (PTS)wheezy1:6.0p1-4+deb7u4vulnerable
wheezy (security)1:6.0p1-4+deb7u6fixed
jessie (security), jessie1:6.7p1-5+deb8u3fixed
buster, sid1:7.6p1-2fixed

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs

Suggested to cherry-pick as well:
otherwise the mitigiation isn't very effective for systems with a locked root account.

Search for package or bug name: Reporting problems