# CVE-2016-6210: Information disclosure in n/a > Remote attackers can enumerate valid usernames by exploiting timing differences in password hashing when specific algorithms are used. - **Severity:** Medium 5.9 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 13 Feb 2017 - **Updated:** 29 May 2026 - **Also known as:** ALPINE-CVE-2016-6210, DEBIAN-CVE-2016-6210, DLA-578-1, DSA-3626-1, GHSA-f525-65h3-3qjh, RHSA-2017:2563, UBUNTU-CVE-2016-6210 ## What is CVE-2016-6210? CVE-2016-6210 is a medium-severity vulnerability in OpenSSH, published on 13 Feb 2017. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official 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. Weakness: CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor) ## Which versions are affected by CVE-2016-6210? It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `openssh` | Red Hat:enterprise_linux:6::client | All versions | 0:5.3p1-123.el6_9 | | `openssh-askpass` | Red Hat:enterprise_linux:6::client | All versions | 0:5.3p1-123.el6_9 | | `openssh-clients` | Red Hat:enterprise_linux:6::client | All versions | 0:5.3p1-123.el6_9 | | `openssh-debuginfo` | Red Hat:enterprise_linux:6::client | All versions | 0:5.3p1-123.el6_9 | | `openssh-ldap` | Red Hat:enterprise_linux:6::client | All versions | 0:5.3p1-123.el6_9 | | `openssh-server` | Red Hat:enterprise_linux:6::client | All versions | 0:5.3p1-123.el6_9 | | `pam_ssh_agent_auth` | Red Hat:enterprise_linux:6::client | All versions | 0:0.9.3-123.el6_9 | | `openssh` | Red Hat:enterprise_linux:6::computenode | All versions | 0:5.3p1-123.el6_9 | | `openssh-askpass` | Red Hat:enterprise_linux:6::computenode | All versions | 0:5.3p1-123.el6_9 | | `openssh-clients` | Red Hat:enterprise_linux:6::computenode | All versions | 0:5.3p1-123.el6_9 | | `openssh-debuginfo` | Red Hat:enterprise_linux:6::computenode | All versions | 0:5.3p1-123.el6_9 | | `openssh-ldap` | Red Hat:enterprise_linux:6::computenode | All versions | 0:5.3p1-123.el6_9 | | `openssh-server` | Red Hat:enterprise_linux:6::computenode | All versions | 0:5.3p1-123.el6_9 | | `pam_ssh_agent_auth` | Red Hat:enterprise_linux:6::computenode | All versions | 0:0.9.3-123.el6_9 | | `openssh` | Red Hat:enterprise_linux:6::server | All versions | 0:5.3p1-123.el6_9 | | `openssh-askpass` | Red Hat:enterprise_linux:6::server | All versions | 0:5.3p1-123.el6_9 | | `openssh-clients` | Red Hat:enterprise_linux:6::server | All versions | 0:5.3p1-123.el6_9 | | `openssh-debuginfo` | Red Hat:enterprise_linux:6::server | All versions | 0:5.3p1-123.el6_9 | | `openssh-ldap` | Red Hat:enterprise_linux:6::server | All versions | 0:5.3p1-123.el6_9 | | `openssh-server` | Red Hat:enterprise_linux:6::server | All versions | 0:5.3p1-123.el6_9 | | `pam_ssh_agent_auth` | Red Hat:enterprise_linux:6::server | All versions | 0:0.9.3-123.el6_9 | | `openssh` | Red Hat:enterprise_linux:6::workstation | All versions | 0:5.3p1-123.el6_9 | | `openssh-askpass` | Red Hat:enterprise_linux:6::workstation | All versions | 0:5.3p1-123.el6_9 | | `openssh-clients` | Red Hat:enterprise_linux:6::workstation | All versions | 0:5.3p1-123.el6_9 | | `openssh-debuginfo` | Red Hat:enterprise_linux:6::workstation | All versions | 0:5.3p1-123.el6_9 | | `openssh-ldap` | Red Hat:enterprise_linux:6::workstation | All versions | 0:5.3p1-123.el6_9 | | `openssh-server` | Red Hat:enterprise_linux:6::workstation | All versions | 0:5.3p1-123.el6_9 | | `pam_ssh_agent_auth` | Red Hat:enterprise_linux:6::workstation | All versions | 0:0.9.3-123.el6_9 | Products: OpenSSH. ## How do I fix CVE-2016-6210? Upgrade to a fixed version. ## Is CVE-2016-6210 being exploited? It is not confirmed as exploited in the wild, but public exploit code for CVE-2016-6210 exists. Public exploit code: - OpenSSH Username Enumeration - CVE-2016-6210 (github_poc): https://github.com/justlce/CVE-2016-6210-Exploit - Custom exploit written for enumerating usernames as per CVE-2016-6210 (github_poc): https://github.com/goomdan/CVE-2016-6210-exploit - User name enumeration against SSH daemons affected by CVE-2016-6210. (github_poc): https://github.com/wabiyagi/CVE-2016-6210 - OpenSSHd 7.2p2 - Username Enumeration (exploitdb) - OpenSSH 7.2p2 - Username Enumeration (exploitdb) - https://github.com/samh4cks/CVE-2016-6210-OpenSSH-User-Enumeration (github_poc): https://github.com/samh4cks/CVE-2016-6210-OpenSSH-User-Enumeration ## Other vulnerabilities in OpenSSH - [CVE-2003-0786](https://insights.sbomify.com/CVE-2003-0786/): Auth bypass in n/a (critical 10.0) - [CVE-2003-0693](https://insights.sbomify.com/CVE-2003-0693/): Memory corruption in n/a (critical 10.0) - [CVE-2002-0640](https://insights.sbomify.com/CVE-2002-0640/): Memory corruption in n/a (critical 10.0) - [CVE-2001-0144](https://insights.sbomify.com/CVE-2001-0144/): Integer overflow in n/a (critical 10.0) - [CVE-2000-0999](https://insights.sbomify.com/CVE-2000-0999/): Memory corruption in n/a (critical 10.0) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2016-6210 and fix it if it is affected. What it is: CVE-2016-6210 is a medium-severity vulnerability in OpenSSH, published on 13 Feb 2017. An attacker can exploit it over the internet without logging in, with no action from the victim. Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2016-6210 exists. Affected product: OpenSSH. No package-level version data is available, so check the vendor advisory linked from the reference page. Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2016-6210/ (Markdown: https://insights.sbomify.com/CVE-2016-6210/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2016-6210 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2016-6210 - OSV: https://osv.dev/vulnerability/CVE-2016-6210 --- From sbomify Insights: https://insights.sbomify.com/CVE-2016-6210/ Summaries are generated and may contain mistakes; the official description above is the record.