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    CVE-2016-20012

    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

    Published:Feb 7, 2016
    Last Modified:May 29, 2026
    EPS:Sep 15, 2021
    EPSS Score:0.14603
    CVSS Score:5.3

    Affected Products

    Vendor
    Netapp
    Product
    Clustered Data Ontap
    Vendor
    Netapp
    Product
    Hci Management Node
    Vendor
    Netapp
    Product
    Ontap Select Deploy Administration Utility
    Vendor
    Netapp
    Product
    Solidfire
    Vendor
    Openbsd
    Product
    Openssh

    Exploits

    https://github.com/openssh/openssh-portable/blob/d0fffc88c8fe90c1815c6f4097bc8cbcabc0f3dd/auth2-pubkey.c#L261-L265https://rushter.com/blog/public-ssh-keys/https://github.com/openssh/openssh-portable/blob/d0fffc88c8fe90c1815c6f4097bc8cbcabc0f3dd/auth2-pubkey.c#L261-L265https://rushter.com/blog/public-ssh-keys/https://github.com/openssh/openssh-portable/blob/d0fffc88c8fe90c1815c6f4097bc8cbcabc0f3dd/auth2-pubkey.c#L261-L265https://github.com/arturo-b-cmu/cve-2016-20012https://github.com/aztec-eagle/cve-2016-20012

    Common Attack Pattern Enumeration and Classification (CAPEC)

    CAPEC-116 Excavation
    CAPEC-13 Subverting Environment Variable Values
    CAPEC-169 Footprinting
    CAPEC-189 Black Box Reverse Engineering
    CAPEC-22 Exploiting Trust in Client
    CAPEC-224 Fingerprinting
    CAPEC-285 ICMP Echo Request Ping
    CAPEC-287 TCP SYN Scan
    CAPEC-290 Enumerate Mail Exchange (MX) Records
    CAPEC-291 DNS Zone Transfers
    CAPEC-292 Host Discovery
    CAPEC-293 Traceroute Route Enumeration
    CAPEC-294 ICMP Address Mask Request
    CAPEC-295 Timestamp Request
    CAPEC-296 ICMP Information Request
    CAPEC-297 TCP ACK Ping
    CAPEC-298 UDP Ping
    CAPEC-299 TCP SYN Ping
    CAPEC-300 Port Scanning
    CAPEC-301 TCP Connect Scan
    CAPEC-302 TCP FIN Scan
    CAPEC-303 TCP Xmas Scan
    CAPEC-304 TCP Null Scan
    CAPEC-305 TCP ACK Scan
    CAPEC-306 TCP Window Scan
    CAPEC-307 TCP RPC Scan
    CAPEC-308 UDP Scan
    CAPEC-309 Network Topology Mapping
    CAPEC-310 Scanning for Vulnerable Software
    CAPEC-312 Active OS Fingerprinting
    CAPEC-313 Passive OS Fingerprinting
    CAPEC-317 IP ID Sequencing Probe
    CAPEC-318 IP 'ID' Echoed Byte-Order Probe
    CAPEC-319 IP (DF) 'Don't Fragment Bit' Echoing Probe
    CAPEC-320 TCP Timestamp Probe
    CAPEC-321 TCP Sequence Number Probe
    CAPEC-322 TCP (ISN) Greatest Common Divisor Probe
    CAPEC-323 TCP (ISN) Counter Rate Probe
    CAPEC-324 TCP (ISN) Sequence Predictability Probe
    CAPEC-325 TCP Congestion Control Flag (ECN) Probe
    CAPEC-326 TCP Initial Window Size Probe
    CAPEC-327 TCP Options Probe
    CAPEC-328 TCP 'RST' Flag Checksum Probe
    CAPEC-329 ICMP Error Message Quoting Probe
    CAPEC-330 ICMP Error Message Echoing Integrity Probe
    CAPEC-472 Browser Fingerprinting
    CAPEC-497 File Discovery
    CAPEC-508 Shoulder Surfing
    CAPEC-573 Process Footprinting
    CAPEC-574 Services Footprinting
    CAPEC-575 Account Footprinting
    CAPEC-576 Group Permission Footprinting
    CAPEC-577 Owner Footprinting
    CAPEC-59 Session Credential Falsification through Prediction
    CAPEC-60 Reusing Session IDs (aka Session Replay)
    CAPEC-616 Establish Rogue Location
    CAPEC-643 Identify Shared Files/Directories on System
    CAPEC-646 Peripheral Footprinting
    CAPEC-651 Eavesdropping
    CAPEC-79 Using Slashes in Alternate Encoding

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    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
    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

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High