Description
sshd in OpenSSH before 7.3, when SHA256 or SHA512 are used for user password hashing, uses BLOWFISH hashing on a static password when the username does not exist, which allows remote attackers to enumerate users by leveraging the timing difference between responses when a large password is provided.
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 | 1:7.2p2-6 | — |
| Debian 13 | openssh | 1:7.2p2-6 | — |
| Debian 12 | openssh | 1:7.2p2-6 | — |
| Debian 8 | openssh | 1:6.7p1-5+deb8u3 | DSA-3626-1 |
| Debian 7 | openssh | 1:6.0p1-4+deb7u5 | DLA-578-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 16.04 LTS | openssh | 1:7.2p2-4ubuntu2.1 | USN-3061-1 |
| Ubuntu 14.04 LTS | openssh | 1:6.6p1-2ubuntu2.8 | USN-3061-1 |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 7 | openssh +7 | 7.4p1-11.el7 | RHSA-2017:2029 |
| RHEL 7 | pam_ssh_agent_auth | 0.10.3-1.11.el7 | RHSA-2017:2029 |
| RHEL 6 | openssh +4 | 5.3p1-123.el6_9 | RHSA-2017:2563 |
| RHEL 6 | pam_ssh_agent_auth | 0.9.3-123.el6_9 | RHSA-2017:2563 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 12 SP1 | openssh +1 | 6.6p1-52.1 | SUSE-SU-2016:2280-1 |
| SLES 12 | openssh +1 | 6.6p1-52.1 | SUSE-SU-2016:2280-1 |
| SLES 11 SP4 | openssh | 6.6p1-28.1 | SUSE-SU-2016:2281-1 |
| SLES 11 SP4 | openssh-askpass-gnome | 6.6p1-28.2 | SUSE-SU-2016:2281-1 |
| SLES 11 SP3 | openssh | 6.2p2-0.33.2 | SUSE-SU-2016:2388-1 |
| SLES 11 SP3 | openssh-askpass-gnome | 6.2p2-0.33.5 | SUSE-SU-2016:2388-1 |
| SLES 11 | openssh-openssl1 | 6.6p1-15.1 | SUSE-SU-2016:2555-1 |
Show 7 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES for SAP 12 SP1 | openssh +1 | 6.6p1-52.1 | SUSE-SU-2016:2280-1 |
| SLES for SAP 12 | openssh +1 | 6.6p1-52.1 | SUSE-SU-2016:2280-1 |
| SLES for SAP 11 SP4 | openssh | 6.6p1-28.1 | SUSE-SU-2016:2281-1 |
| SLES for SAP 11 SP4 | openssh-askpass-gnome | 6.6p1-28.2 | SUSE-SU-2016:2281-1 |
| SUSE OpenStack Cloud 5 | openssh | 6.2p2-0.33.2 | SUSE-SU-2016:2388-1 |
| SUSE OpenStack Cloud 5 | openssh-askpass-gnome | 6.2p2-0.33.5 | SUSE-SU-2016:2388-1 |
| SUSE Manager Proxy 2.1 | openssh | 6.2p2-0.33.2 | SUSE-SU-2016:2388-1 |
| SUSE Manager Proxy 2.1 | openssh-askpass-gnome | 6.2p2-0.33.5 | SUSE-SU-2016:2388-1 |
| SUSE Manager 2.1 | openssh | 6.2p2-0.33.2 | SUSE-SU-2016:2388-1 |
| SUSE Manager 2.1 | openssh-askpass-gnome | 6.2p2-0.33.5 | SUSE-SU-2016:2388-1 |
| SUSE Linux Enterprise Point of Sale 11 SP3 | openssh | 6.2p2-0.33.2 | SUSE-SU-2016:2388-1 |
| SUSE Linux Enterprise Point of Sale 11 SP3 | openssh-askpass-gnome | 6.2p2-0.33.5 | SUSE-SU-2016:2388-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | openssh | 7.2p2-3.1 | openSUSE-SU-2024:10174-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.4 | openssh | 7.2_p2-r1 | — |
| Alpine v3.3 | openssh | 7.2_p2-r1 | — |
| Alpine v3.2 | openssh | 6.8_p1-r7 | — |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 7 | openssh +7 | 7.4p1-11.el7 | ELSA-2017-2029 |
| Oracle Linux 7 | pam_ssh_agent_auth | 0.10.3-1.11.el7 | ELSA-2017-2029 |
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.
Third-party code, not reviewed by us. Public PoCs are sometimes fake or contain malware. Read the code first and run it only in an isolated lab, against systems you are authorised to test.
Metasploit 1 module
-
SSH Username Enumeration
auxiliary/scanner/ssh/ssh_enumusers
Exploit-DB 2
- OpenSSH 7.2p2 - Username Enumeration EDB-40136 · remote · Jul 20, 2016
- OpenSSHd 7.2p2 - Username Enumeration EDB-40113 · remote · Jul 18, 2016
GitHub 7 repositories
-
justlce/CVE-2016-6210-Exploit ★ 3 · Aug 25, 2019
OpenSSH Username Enumeration - CVE-2016-6210
-
Alisha-chaudhary/ssh-enum ★ 2 · Apr 30, 2026
This project explores whether modern OpenSSH reveals valid usernames through subtle response or timing differences. CVE-2016-6210 user enumeration investigation ( Welch's t-test, Cohen's d, and detec…
-
wabiyagi/CVE-2016-6210 ★ 1 · Mar 14, 2025
User name enumeration against SSH daemons affected by CVE-2016-6210.
-
goomdan/CVE-2016-6210-exploit ★ 1 · Mar 19, 2023
Custom exploit written for enumerating usernames as per CVE-2016-6210
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KiPhuong/cve-2016-6210 ★ 0 · Jul 17, 2025
PoC of cve-2016-6210
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nicoleman0/CVE-2016-6210-OpenSSHd-7.2p2 ★ 0 · Apr 12, 2025
-
samh4cks/CVE-2016-6210-OpenSSH-User-Enumeration ★ 0 · Sep 1, 2023
Sources: PoC-in-GitHub, Metasploit Framework, Exploit-DB — updated daily. Only links are listed; no exploit code is hosted here.
Advisories 14
- RHSA-2017:2029 Red Hat Security Advisory: openssh security, bug fix, and enhancement update Red Hat Security Advisories (RHSA) · Jun 26, 2026
- RHSA-2017:2563 Red Hat Security Advisory: openssh security update Red Hat Security Advisories (RHSA) · Jun 26, 2026
- USN-3061-1 openssh vulnerabilities Ubuntu Security Notices (USN) · Jun 1, 2026
- DLA-578-1 openssh - security update Debian Security (DSA / DLA) · Mar 9, 2026
- DSA-3626-1 openssh - security update Debian Security (DSA / DLA) · Mar 9, 2026
- openSUSE-SU-2024:10174-1 openssh-7.2p2-3.1 on GA media SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2016:2281-1 Security update for openssh SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2016:2555-1 Security update for openssh-openssl1 SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2016:2280-1 Security update for openssh SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2016:2388-1 Security update for openssh SUSE / openSUSE Security Updates · Feb 4, 2026
- WID-SEC-2023-0450 OpenSSH: Schwachstelle ermöglicht Offenlegung von Informationen BSI CERT-Bund (WID) · May 7, 2024
- ICSA-22-349-21 Siemens SCALANCE X-200RNA Switch Devices CISA ICS & IT advisories · Dec 13, 2022
- SSA-412672 SSA-412672: Multiple OpenSSL and OpenSSH Vulnerabilities in SCALANCE X-200RNA Switch Devices before V3.2.7 Siemens ProductCERT · Dec 13, 2022
- ELSA-2017-2029 Moderate: openssh security, bug fix, and enhancement update (Oracle Linux 7) Oracle Linux Security Advisories (ELSA) · Aug 7, 2017
References
- RHSA-2017:2563 vendor-advisory
- 1036319 vdb-entry
- 20160714 opensshd - user enumeration mailing-list
- DSA-3626 vendor-advisory
- 40136 exploit
- 40113 exploit
- https://www.openssh.com/txt/release-7.3
- GLSA-201612-18 vendor-advisory
- RHSA-2017:2029 vendor-advisory
- 91812 vdb-entry
- https://security.netapp.com/advisory/ntap-20190206-0001/
- https://cert-portal.siemens.com/productcert/pdf/ssa-412672.pdf