{"id":"UBUNTU-CVE-2016-20012","details":"OpenSSH through 8.7 allows remote attackers, who have a suspicion that a certain combination of username and public key is known to an SSH server, to test whether this suspicion is correct. This occurs because a challenge is sent only when that combination could be valid for a login session. NOTE: the vendor does not recognize user enumeration as a vulnerability for this product","modified":"2026-04-30T09:25:03.285045Z","published":"2021-09-15T20:15:00Z","upstream":["CVE-2016-20012"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2016-20012"},{"type":"REPORT","url":"https://github.com/openssh/openssh-portable/pull/270"},{"type":"REPORT","url":"https://github.com/openssh/openssh-portable/blob/d0fffc88c8fe90c1815c6f4097bc8cbcabc0f3dd/auth2-pubkey.c#L261-L265"},{"type":"REPORT","url":"https://rushter.com/blog/public-ssh-keys/"},{"type":"REPORT","url":"https://utcc.utoronto.ca/~cks/space/blog/tech/SSHKeysAreInfoLeak"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2016-20012"}],"affected":[{"package":{"name":"openssh","ecosystem":"Ubuntu:Pro:14.04:LTS","purl":"pkg:deb/ubuntu/openssh@1:6.6p1-2ubuntu2.13+esm2?arch=source&distro=esm-infra-legacy/trusty"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1:6.2p2-6","1:6.2p2-6ubuntu1","1:6.4p1-1","1:6.4p1-2","1:6.5p1-1","1:6.5p1-2","1:6.5p1-3","1:6.5p1-4","1:6.5p1-6","1:6.6p1-1","1:6.6p1-2","1:6.6p1-2ubuntu1","1:6.6p1-2ubuntu2","1:6.6p1-2ubuntu2.2","1:6.6p1-2ubuntu2.3","1:6.6p1-2ubuntu2.4","1:6.6p1-2ubuntu2.6","1:6.6p1-2ubuntu2.7","1:6.6p1-2ubuntu2.8","1:6.6p1-2ubuntu2.10","1:6.6p1-2ubuntu2.11","1:6.6p1-2ubuntu2.12","1:6.6p1-2ubuntu2.13","1:6.6p1-2ubuntu2.13+esm1","1:6.6p1-2ubuntu2.13+esm2"],"ecosystem_specific":{"binaries":[{"binary_name":"openssh-client","binary_version":"1:6.6p1-2ubuntu2.13+esm2"},{"binary_name":"openssh-server","binary_version":"1:6.6p1-2ubuntu2.13+esm2"},{"binary_name":"openssh-sftp-server","binary_version":"1:6.6p1-2ubuntu2.13+esm2"},{"binary_name":"ssh","binary_version":"1:6.6p1-2ubuntu2.13+esm2"},{"binary_name":"ssh-askpass-gnome","binary_version":"1:6.6p1-2ubuntu2.13+esm2"},{"binary_name":"ssh-krb5","binary_version":"1:6.6p1-2ubuntu2.13+esm2"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2016/UBUNTU-CVE-2016-20012.json"}},{"package":{"name":"openssh","ecosystem":"Ubuntu:Pro:16.04:LTS","purl":"pkg:deb/ubuntu/openssh@1:7.2p2-4ubuntu2.10+esm7?arch=source&distro=esm-infra/xenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1:6.9p1-2","1:6.9p1-3","1:7.1p1-1","1:7.1p1-3","1:7.1p1-4","1:7.1p1-6","1:7.1p2-1","1:7.1p2-2","1:7.2p1-1","1:7.2p2-1","1:7.2p2-2","1:7.2p2-3","1:7.2p2-4","1:7.2p2-4ubuntu1","1:7.2p2-4ubuntu2.1","1:7.2p2-4ubuntu2.2","1:7.2p2-4ubuntu2.4","1:7.2p2-4ubuntu2.5","1:7.2p2-4ubuntu2.6","1:7.2p2-4ubuntu2.7","1:7.2p2-4ubuntu2.8","1:7.2p2-4ubuntu2.10","1:7.2p2-4ubuntu2.10+esm1","1:7.2p2-4ubuntu2.10+esm2","1:7.2p2-4ubuntu2.10+esm3","1:7.2p2-4ubuntu2.10+esm4","1:7.2p2-4ubuntu2.10+esm5","1:7.2p2-4ubuntu2.10+esm6","1:7.2p2-4ubuntu2.10+esm7"],"ecosystem_specific":{"binaries":[{"binary_name":"openssh-client","binary_version":"1:7.2p2-4ubuntu2.10+esm7"},{"binary_name":"openssh-client-ssh1","binary_version":"1:7.2p2-4ubuntu2.10+esm7"},{"binary_name":"openssh-server","binary_version":"1:7.2p2-4ubuntu2.10+esm7"},{"binary_name":"openssh-sftp-server","binary_version":"1:7.2p2-4ubuntu2.10+esm7"},{"binary_name":"ssh","binary_version":"1:7.2p2-4ubuntu2.10+esm7"},{"binary_name":"ssh-askpass-gnome","binary_version":"1:7.2p2-4ubuntu2.10+esm7"},{"binary_name":"ssh-krb5","binary_version":"1:7.2p2-4ubuntu2.10+esm7"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2016/UBUNTU-CVE-2016-20012.json"}},{"package":{"name":"openssh","ecosystem":"Ubuntu:Pro:FIPS:16.04:LTS","purl":"pkg:deb/ubuntu/openssh@1:7.2p2-4ubuntu2.fips.2.10.7?arch=source&distro=fips-updates/xenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1:7.2p2-4ubuntu2.fips.2.2.3","1:7.2p2-4ubuntu2.fips.2.4.1","1:7.2p2-4ubuntu2.fips.2.4.2","1:7.2p2-4ubuntu2.fips.2.8.1","1:7.2p2-4ubuntu2.fips.2.10.1","1:7.2p2-4ubuntu2.fips.2.10.2","1:7.2p2-4ubuntu2.fips.2.10.3","1:7.2p2-4ubuntu2.fips.2.10.4","1:7.2p2-4ubuntu2.fips.2.10.5","1:7.2p2-4ubuntu2.fips.2.10.6","1:7.2p2-4ubuntu2.fips.2.10.7"],"ecosystem_specific":{"binaries":[{"binary_name":"openssh-client","binary_version":"1:7.2p2-4ubuntu2.fips.2.10.7"},{"binary_name":"openssh-client-hmac","binary_version":"1:7.2p2-4ubuntu2.fips.2.10.7"},{"binary_name":"openssh-client-ssh1","binary_version":"1:7.2p2-4ubuntu2.fips.2.10.7"},{"binary_name":"openssh-server","binary_version":"1:7.2p2-4ubuntu2.fips.2.10.7"},{"binary_name":"openssh-server-hmac","binary_version":"1:7.2p2-4ubuntu2.fips.2.10.7"},{"binary_name":"openssh-sftp-server","binary_version":"1:7.2p2-4ubuntu2.fips.2.10.7"},{"binary_name":"ssh","binary_version":"1:7.2p2-4ubuntu2.fips.2.10.7"},{"binary_name":"ssh-askpass-gnome","binary_version":"1:7.2p2-4ubuntu2.fips.2.10.7"},{"binary_name":"ssh-krb5","binary_version":"1:7.2p2-4ubuntu2.fips.2.10.7"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2016/UBUNTU-CVE-2016-20012.json"}},{"package":{"name":"openssh","ecosystem":"Ubuntu:Pro:FIPS:16.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