CVE-2016-20012
OpenSSH through 8.7 allows remote attackers, who have a suspicion that a certain combination of...
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
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- Low
- Integrity
- None
- Availability
- None
Exploit likelihood
What each source reports
NVD Score used
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
- Record
CVE-2016-20012- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N - CVSS 2.0
- 4.3 Medium
AV:N/AC:M/Au:N/C:P/I:N/A:N - Weakness
- CWE-203
- Updated
- 2026-11-02
CVE List
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
- Record
CVE-2016-20012- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N - Weakness
- CWE-203
- Updated
- 2026-11-02
EUVDEUVD-2016-3100
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
- Record
EUVD-2016-3100- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-84j4-ccmw-hwpg
OpenSSH through 8.7 allows remote attackers, who have a suspicion that a certain combination of...
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.
- Record
GHSA-84j4-ccmw-hwpg- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N - Weakness
- CWE-203
- Updated
- 2026-11-02
OSVBELL-CVE-2016-20012
CVE-2016-20012 does not affect BellSoft software
- Record
BELL-CVE-2016-20012- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N - Updated
- 2026-11-02
OSV
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
- Record
CVE-2016-20012- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N - Updated
- 2026-11-02
OSVDEBIAN-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
- Record
DEBIAN-CVE-2016-20012- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N - Updated
- 2026-11-02
OSVUBUNTU-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
- Record
UBUNTU-CVE-2016-20012- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N - Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
opensshDebian:12 |
All versions, plus listed versions 1:10.0p1-11:10.0p1-21:10.0p1-31:10.0p1-41:10.0p1-5 Show 45 moreShow less1:10.0p1-5~bpo12+21:10.0p1-61:10.0p1-71:10.0p1-7~bpo12+11:10.0p1-81:10.1p1-11:10.1p1-21:10.2p1-11:10.2p1-21:10.2p1-2~bpo13+11:10.2p1-31:10.2p1-41:10.2p1-51:10.2p1-61:10.2p1-6~bpo13+11:10.3p1-11:10.3p1-1~bpo13+11:10.3p1-21:10.3p1-31:10.3p1-41:10.3p1-51:10.3p1-71:10.3p1-81:10.3p1-91:10.4p1-11:10.4p1-21:10.4p1-31:10.4p1-41:10.4p1-51:10.5p1-11:9.2p1-21:9.2p1-2+deb12u11:9.2p1-2+deb12u101:9.2p1-2+deb12u21:9.2p1-2+deb12u31:9.2p1-2+deb12u41:9.2p1-2+deb12u51:9.2p1-2+deb12u61:9.2p1-2+deb12u71:9.2p1-2+deb12u81:9.2p1-2+deb12u91:9.3p1-11:9.3p1-1+loong641:9.3p2-11:9.4p1-1 |
None known |
opensshDebian:13 |
All versions, plus listed versions 1:10.0p1-71:10.0p1-7+deb13u11:10.0p1-7+deb13u21:10.0p1-7+deb13u31:10.0p1-7+deb13u4 Show 26 moreShow less1:10.0p1-81:10.1p1-11:10.1p1-21:10.2p1-11:10.2p1-21:10.2p1-2~bpo13+11:10.2p1-31:10.2p1-41:10.2p1-51:10.2p1-61:10.2p1-6~bpo13+11:10.3p1-11:10.3p1-1~bpo13+11:10.3p1-21:10.3p1-31:10.3p1-41:10.3p1-51:10.3p1-71:10.3p1-81:10.3p1-91:10.4p1-11:10.4p1-21:10.4p1-31:10.4p1-41:10.4p1-51:10.5p1-1 |
None known |
opensshDebian:14 |
All versions, plus listed versions 1:10.0p1-71:10.0p1-81:10.1p1-11:10.1p1-21:10.2p1-1 Show 22 moreShow less1:10.2p1-21:10.2p1-2~bpo13+11:10.2p1-31:10.2p1-41:10.2p1-51:10.2p1-61:10.2p1-6~bpo13+11:10.3p1-11:10.3p1-1~bpo13+11:10.3p1-21:10.3p1-31:10.3p1-41:10.3p1-51:10.3p1-71:10.3p1-81:10.3p1-91:10.4p1-11:10.4p1-21:10.4p1-31:10.4p1-41:10.4p1-51:10.5p1-1 |
None known |
opensshUbuntu:Pro:14.04:LTS |
All versions, plus listed versions 1:6.2p2-61:6.2p2-6ubuntu11:6.4p1-11:6.4p1-21:6.5p1-1 Show 22 moreShow less1:6.5p1-21:6.5p1-31:6.5p1-41:6.5p1-61:6.6p1-11:6.6p1-21:6.6p1-2ubuntu11:6.6p1-2ubuntu21:6.6p1-2ubuntu2.21:6.6p1-2ubuntu2.31:6.6p1-2ubuntu2.41:6.6p1-2ubuntu2.61:6.6p1-2ubuntu2.71:6.6p1-2ubuntu2.81:6.6p1-2ubuntu2.101:6.6p1-2ubuntu2.111:6.6p1-2ubuntu2.121:6.6p1-2ubuntu2.131:6.6p1-2ubuntu2.13+esm11:6.6p1-2ubuntu2.13+esm21:6.6p1-2ubuntu2.13+esm31:6.6p1-2ubuntu2.13+esm4 |
None known |
opensshUbuntu:Pro:16.04:LTS |
All versions, plus listed versions 1:6.9p1-21:6.9p1-31:7.1p1-11:7.1p1-31:7.1p1-4 Show 27 moreShow less1:7.1p1-61:7.1p2-11:7.1p2-21:7.2p1-11:7.2p2-11:7.2p2-21:7.2p2-31:7.2p2-41:7.2p2-4ubuntu11:7.2p2-4ubuntu2.11:7.2p2-4ubuntu2.21:7.2p2-4ubuntu2.41:7.2p2-4ubuntu2.51:7.2p2-4ubuntu2.61:7.2p2-4ubuntu2.71:7.2p2-4ubuntu2.81:7.2p2-4ubuntu2.101:7.2p2-4ubuntu2.10+esm11:7.2p2-4ubuntu2.10+esm21:7.2p2-4ubuntu2.10+esm31:7.2p2-4ubuntu2.10+esm41:7.2p2-4ubuntu2.10+esm51:7.2p2-4ubuntu2.10+esm61:7.2p2-4ubuntu2.10+esm71:7.2p2-4ubuntu2.10+esm81:7.2p2-4ubuntu2.10+esm91:7.2p2-4ubuntu2.10+esm10 |
None known |
opensshUbuntu:Pro:FIPS-updates:16.04:LTS |
All versions, plus listed versions 1:7.2p2-4ubuntu2.fips.2.2.31:7.2p2-4ubuntu2.fips.2.4.11:7.2p2-4ubuntu2.fips.2.4.21:7.2p2-4ubuntu2.fips.2.8.11:7.2p2-4ubuntu2.fips.2.10.1 Show 6 moreShow less1:7.2p2-4ubuntu2.fips.2.10.21:7.2p2-4ubuntu2.fips.2.10.31:7.2p2-4ubuntu2.fips.2.10.41:7.2p2-4ubuntu2.fips.2.10.51:7.2p2-4ubuntu2.fips.2.10.61:7.2p2-4ubuntu2.fips.2.10.7 |
None known |
opensshUbuntu:Pro:FIPS:16.04:LTS |
All versions, plus listed versions 1:7.2p2-4ubuntu2.fips.2.21:7.2p2-4ubuntu2.fips.2.2.11:7.2p2-4ubuntu2.fips.2.10.1 |
None known |
opensshUbuntu:Pro:18.04:LTS |
All versions, plus listed versions 1:7.5p1-101:7.6p1-41:7.6p1-4ubuntu0.11:7.6p1-4ubuntu0.21:7.6p1-4ubuntu0.3 Show 9 moreShow less1:7.6p1-4ubuntu0.51:7.6p1-4ubuntu0.61:7.6p1-4ubuntu0.71:7.6p1-4ubuntu0.7+esm11:7.6p1-4ubuntu0.7+esm21:7.6p1-4ubuntu0.7+esm31:7.6p1-4ubuntu0.7+esm41:7.6p1-4ubuntu0.7+esm51:7.6p1-4ubuntu0.7+esm6 |
None known |
openssh-ssh1Ubuntu:18.04:LTS |
All versions, plus listed versions 1:7.5p1-81:7.5p1-91:7.5p1-9build11:7.5p1-10 |
None known |
opensshUbuntu:Pro:FIPS-updates:18.04:LTS |
All versions, plus listed versions 1:7.9p1-10~ubuntu18.04.fips.0.11:7.9p1-10~ubuntu18.04.fips.0.21:7.9p1-10~ubuntu18.04.fips.0.31:7.9p1-10~ubuntu18.04.fips.0.41:7.9p1-10~ubuntu18.04.fips.0.5 Show 5 moreShow less1:7.9p1-10~ubuntu18.04.fips.0.61:7.9p1-10~ubuntu18.04.fips.0.71:7.9p1-10~ubuntu18.04.fips.0.81:7.9p1-10~ubuntu18.04.fips.0.91:7.9p1-10~ubuntu18.04.fips.0.10 |
None known |
Show 7 moreShow less
| Package | Affected | Fixed |
|---|---|---|
opensshUbuntu:Pro:FIPS:18.04:LTS |
All versions, plus listed versions 1:7.9p1-10~ubuntu18.04.fips.0.11:7.9p1-10~ubuntu18.04.fips.0.2 |
None known |
opensshUbuntu:Pro:20.04:LTS |
All versions, plus listed versions 1:8.0p1-6build11:8.1p1-11:8.1p1-51:8.2p1-41:8.2p1-4ubuntu0.1 Show 14 moreShow less1:8.2p1-4ubuntu0.21:8.2p1-4ubuntu0.31:8.2p1-4ubuntu0.41:8.2p1-4ubuntu0.51:8.2p1-4ubuntu0.71:8.2p1-4ubuntu0.81:8.2p1-4ubuntu0.91:8.2p1-4ubuntu0.101:8.2p1-4ubuntu0.111:8.2p1-4ubuntu0.121:8.2p1-4ubuntu0.131:8.2p1-4ubuntu0.13+esm11:8.2p1-4ubuntu0.13+esm21:8.2p1-4ubuntu0.13+esm3 |
None known |
openssh-ssh1Ubuntu:20.04:LTS |
All versions, plus listed versions 1:7.5p1-11build1 |
None known |
opensshUbuntu:Pro:FIPS-updates:20.04:LTS |
All versions, plus listed versions 1:8.2p1-4ubuntu0.fips.0.2.11:8.2p1-4ubuntu0.fips.0.4.01:8.2p1-4ubuntu0.fips.0.5.01:8.2p1-4ubuntu0.fips.0.71:8.2p1-4ubuntu0.fips.0.8 Show 7 moreShow less1:8.2p1-4ubuntu0.fips.0.91:8.2p1-4ubuntu0.fips.0.101:8.2p1-4ubuntu0.fips.0.111:8.2p1-4ubuntu0.fips.0.121:8.2p1-4ubuntu0.fips.0.131:8.2p1-4ubuntu0.fips.0.13.11:8.2p1-4ubuntu0.fips.0.13.3 |
None known |
opensshUbuntu:Pro:FIPS:20.04:LTS |
All versions, plus listed versions 1:8.2p1-4ubuntu0.fips.0.2.1 |
None known |
opensshUbuntu:22.04:LTS |
All versions, plus listed versions 1:8.4p1-6ubuntu21:8.7p1-21:8.7p1-2build11:8.7p1-41:8.8p1-1 Show 15 moreShow less1:8.9p1-31:8.9p1-3ubuntu0.11:8.9p1-3ubuntu0.31:8.9p1-3ubuntu0.41:8.9p1-3ubuntu0.51:8.9p1-3ubuntu0.61:8.9p1-3ubuntu0.71:8.9p1-3ubuntu0.101:8.9p1-3ubuntu0.111:8.9p1-3ubuntu0.131:8.9p1-3ubuntu0.141:8.9p1-3ubuntu0.151:8.9p1-3ubuntu0.161:8.9p1-3ubuntu0.171:8.9p1-3ubuntu0.18 |
None known |
openssh-ssh1Ubuntu:22.04:LTS |
All versions, plus listed versions 1:7.5p1-121:7.5p1-12build11:7.5p1-13 |
None known |
Public exploits
Links only. Every CVE stores no exploit code.
| Source | Link | Date |
|---|---|---|
| PoC in GitHub | arturo-b-cmu/cve-2016-20012 | 2024-08-28 |
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, GitHub Advisories, NVD, OSV, PoC in GitHub |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2016-20012 is a medium vulnerability (CVSS 5.3) in Openbsd Openssh, published September 15, 2021. Its validity is disputed. Public exploit code exists. EPSS puts the chance of exploitation in the next 30 days at 5.33%, the 92nd percentile.
References
github.com/openssh/openssh-portable/pull/270
utcc.utoronto.ca/~cks/space/blog/tech/SSHKeysAreInfoLeak
rushter.com/blog/public-ssh-keys
security.netapp.com/advisory/ntap-20211014-0005
openwall.com/lists/oss-security/2018/08/24/1
Left out here: 27 versions. The JSON record has them.