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
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | openssh | No fix yet | — |
| Debian 13 | openssh | No fix yet | — |
| Debian 12 | openssh | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 22.04 LTS | openssh +1 | No fix yet | — |
| Ubuntu 20.04 LTS | openssh-ssh1 | No fix yet | — |
| Ubuntu 18.04 LTS | openssh-ssh1 | No fix yet | — |
Show 10 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro FIPS 20.04 LTS | openssh | No fix yet | — |
| Ubuntu Pro FIPS 18.04 LTS | openssh | No fix yet | — |
| Ubuntu Pro FIPS 16.04 LTS | openssh | No fix yet | — |
| Ubuntu Pro FIPS-updates 20.04 LTS | openssh | No fix yet | — |
| Ubuntu Pro FIPS-updates 18.04 LTS | openssh | No fix yet | — |
| Ubuntu Pro FIPS-updates 16.04 LTS | openssh | No fix yet | — |
| Ubuntu Pro 20.04 LTS | openssh | No fix yet | — |
| Ubuntu Pro 18.04 LTS | openssh | No fix yet | — |
| Ubuntu Pro 16.04 LTS | openssh | No fix yet | — |
| Ubuntu Pro 14.04 LTS | openssh | No fix yet | — |
Public exploits
Exploit or proof-of-concept code for this vulnerability is publicly available, which lowers the bar for attackers. Treat it as a reason to patch sooner.
GitHub 1 repository
-
arturo-b-cmu/cve-2016-20012 ★ 0 · Aug 28, 2024
Sources: PoC-in-GitHub, Metasploit Framework, Exploit-DB — updated daily. Only links are listed; no exploit code is hosted here.
Advisories 5
- SCA-2025-0011 Vulnerabilities affecting Endress+Hauser SSG-E210GC SICK PSIRT · Oct 2, 2025
- SCA-2025-0009 Vulnerabilities affecting SICK TDC-E210GC SICK PSIRT · Aug 1, 2025
- VDE-2022-010 PHOENIX CONTACT: Multiple Linux component vulnerabilities fixed in latest AXC F x152 LTS release CERT@VDE · May 22, 2025
- WID-SEC-2024-1082 Juniper JUNOS: Mehrere Schwachstellen BSI CERT-Bund (WID) · May 9, 2024
- WID-SEC-2024-0229 OpenSSH: Schwachstelle ermöglicht Offenlegung von Informationen BSI CERT-Bund (WID) · Jan 28, 2024
References
- https://github.com/openssh/openssh-portable/pull/270
- https://github.com/openssh/openssh-portable/blob/d0fffc88c8fe90c1815c6f4097bc8cbcabc0f3dd/auth2-pubkey.c#L261-L265
- https://utcc.utoronto.ca/~cks/space/blog/tech/SSHKeysAreInfoLeak
- https://rushter.com/blog/public-ssh-keys/
- https://security.netapp.com/advisory/ntap-20211014-0005/
- https://github.com/openssh/openssh-portable/pull/270#issuecomment-920577097
- https://www.openwall.com/lists/oss-security/2018/08/24/1
- https://github.com/openssh/openssh-portable/pull/270#issuecomment-943909185