CVE-2016-20012

Severity: medium (CVSS 5.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 5.3% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2021-09-15 · updated 2026-06-17
Weakness: CWE-203

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

Affected products

Clustered Data ONTAP: all versions
NetApp Hci Management Node: all versions
NetApp ONTAP Select Deploy administration utility: all versions
NetApp Solidfire: all versions
OpenSSH: through 8.7

References

https://github.com/openssh/openssh-portable/blob/d0fffc88c8fe90c1815c6f4097bc8cbcabc0f3dd/auth2-pubkey.c#L261-L265
https://github.com/openssh/openssh-portable/pull/270
https://github.com/openssh/openssh-portable/pull/270#issuecomment-920577097
https://github.com/openssh/openssh-portable/pull/270#issuecomment-943909185
https://rushter.com/blog/public-ssh-keys/
https://security.netapp.com/advisory/ntap-20211014-0005/
https://utcc.utoronto.ca/~cks/space/blog/tech/SSHKeysAreInfoLeak
https://www.openwall.com/lists/oss-security/2018/08/24/1
https://github.com/openssh/openssh-portable/blob/d0fffc88c8fe90c1815c6f4097bc8cbcabc0f3dd/auth2-pubkey.c#L261-L265
https://github.com/openssh/openssh-portable/pull/270
https://github.com/openssh/openssh-portable/pull/270#issuecomment-920577097
https://github.com/openssh/openssh-portable/pull/270#issuecomment-943909185

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