CVE-2016-20012
13Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 5.3epss 5.3%
exploitation probability
5.3%top 8% of all CVEs
observed exploitation
nono source reports it
In short
OpenSSH reveals whether a username and public key combination is valid on a server by sending a challenge only for known combinations. This allows attackers to enumerate valid usernames without needing the actual password.
Technical detail
CWE-203 information disclosure vulnerability in OpenSSH through version 8.7: the server sends authentication challenges only for valid username-public key pairs, enabling remote attackers to enumerate valid user accounts through timing or response analysis. Requires network access to SSH service; no authentication needed for reconnaissance.
Summary generated and translated by AI from the official description.
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
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Affected products
n/a · n/aReferences
https://github.com/openssh/openssh-portable/blob/d0fffc88c8fe90c1815c6f4097bc8cbcabc0f3dd/auth2-pubkey.c#L261-L265https://github.com/openssh/openssh-portable/pull/270https://github.com/openssh/openssh-portable/pull/270#issuecomment-920577097https://github.com/openssh/openssh-portable/pull/270#issuecomment-943909185https://rushter.com/blog/public-ssh-keys/https://security.netapp.com/advisory/ntap-20211014-0005/https://utcc.utoronto.ca/~cks/space/blog/tech/SSHKeysAreInfoLeakhttps://www.openwall.com/lists/oss-security/2018/08/24/1