CVE-2016-6210

MEDIUM

OpenSSH < 7.2 - User Enumeration via Timing Attack on Password Hashing

Title source: llm
STIX 2.1

Exploitation Summary

EIP tracks 12 public exploits for CVE-2016-6210. PoCs published by 0_o, Eddie Harari, justlce.

AI-analyzed exploit summary This exploit leverages a timing attack in OpenSSH (CVE-2016-6210) to enumerate valid usernames by measuring authentication response times. It sends a large password payload and compares timing differences between valid and invalid users.

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.

Exploits (12)

exploitdb WORKING POC
by 0_o · pythonremotelinux
https://www.exploit-db.com/exploits/40136

This exploit leverages a timing attack in OpenSSH (CVE-2016-6210) to enumerate valid usernames by measuring authentication response times. It sends a large password payload and compares timing differences between valid and invalid users.

Classification
Working Poc 95%
Attack Type
Info Leak
Complexity
Moderate
Reliability
Reliable
Target: OpenSSH (versions affected by CVE-2016-6210)
No auth needed
Prerequisites: Network access to the SSH daemon
devstral-2 · analyzed Feb 16, 2026 Full analysis →
exploitdb WORKING POC
by Eddie Harari · textremotelinux
https://www.exploit-db.com/exploits/40113

This exploit leverages timing differences in SSH authentication to enumerate valid users by sending large passwords (10KB), causing slower response times for valid users due to SHA256/SHA512 hashing compared to BLOWFISH for non-existent users.

Classification
Working Poc 90%
Attack Type
Info Leak
Complexity
Trivial
Reliability
Reliable
Target: OpenSSH <=7.2p2
No auth needed
Prerequisites: Network access to target SSH server · SSH server with password authentication enabled
devstral-2 · analyzed Feb 16, 2026 Full analysis →
nomisec WORKING POC 3 stars
by justlce · poc
https://github.com/justlce/CVE-2016-6210-Exploit

This repository contains functional exploit code for CVE-2016-6210, a timing-based user enumeration vulnerability in OpenSSH. The exploit leverages the difference in response times when authenticating with large passwords for valid vs. invalid users due to differing hash algorithms (SHA256/SHA512 vs. BLOWFISH).

Classification
Working Poc 95%
Attack Type
Info Leak
Complexity
Moderate
Reliability
Reliable
Target: OpenSSH (tested on OpenSSH_6.9p1 and opensshd-7.2p2)
No auth needed
Prerequisites: Network access to the target SSH server · List of usernames to test
devstral-2 · analyzed Feb 18, 2026 Full analysis →
nomisec WORKING POC 1 stars
by serexp · poc
https://github.com/serexp/poc-CVE20166210

This repository contains a functional Python script that exploits CVE-2016-6210, a timing side-channel vulnerability in OpenSSH 7.2p2, to enumerate valid usernames via differential response times during authentication attempts.

Classification
Working Poc 95%
Attack Type
Info Leak
Complexity
Moderate
Reliability
Reliable
Target: OpenSSH 7.2p2
No auth needed
Prerequisites: network access to the SSH daemon · Python with paramiko and numpy libraries
devstral-2 · analyzed May 19, 2026 Full analysis →
nomisec SCANNER 1 stars
by wabiyagi · poc
https://github.com/wabiyagi/CVE-2016-6210

This repository contains a Python script that performs user name enumeration against SSH daemons affected by CVE-2016-6210 by exploiting a timing side-channel vulnerability. It measures the time taken to respond to authentication attempts with non-existent users versus potential valid users.

Classification
Scanner 95%
Attack Type
Info Leak
Complexity
Moderate
Reliability
Reliable
Target: OpenSSH (versions affected by CVE-2016-6210)
No auth needed
Prerequisites: network access to the target SSH server · list of potential usernames or a single username to test
devstral-2 · analyzed Apr 29, 2026 Full analysis →
nomisec WORKING POC 1 stars
by goomdan · poc
https://github.com/goomdan/CVE-2016-6210-exploit

This repository contains a functional Python exploit for CVE-2016-6210, which leverages timing differences in OpenSSH's password hashing to enumerate valid usernames. The exploit sends large passwords (25KB) to measure response times, identifying valid users based on longer processing delays.

Classification
Working Poc 95%
Attack Type
Info Leak
Complexity
Moderate
Reliability
Reliable
Target: OpenSSH versions before 7.3
No auth needed
Prerequisites: Network access to the target SSH server · A wordlist of potential usernames
devstral-2 · analyzed Feb 18, 2026 Full analysis →
nomisec WORKING POC 1 stars
by samh4cks · poc
https://github.com/samh4cks/CVE-2016-6210-OpenSSH-User-Enumeration

This Python script exploits CVE-2016-6210, a timing-based user enumeration vulnerability in OpenSSH. It measures authentication response times to distinguish valid users from invalid ones by leveraging the delay difference caused by the flaw.

Classification
Working Poc 95%
Attack Type
Info Leak
Complexity
Moderate
Reliability
Reliable
Target: OpenSSH (versions affected by CVE-2016-6210)
No auth needed
Prerequisites: Network access to the target SSH server · Paramiko library installed
devstral-2 · analyzed Feb 18, 2026 Full analysis →
nomisec WORKING POC
by Alisha-chaudhary · poc
https://github.com/Alisha-chaudhary/ssh-enum

This repository contains a functional exploit PoC for CVE-2016-6210, which is a timing side-channel vulnerability in OpenSSH that allows user enumeration. The code includes tools for banner fingerprinting, manual SSH probing with timing analysis, and Metasploit integration to detect valid usernames.

Classification
Working Poc 95%
Attack Type
Info Leak
Complexity
Moderate
Reliability
Reliable
Target: OpenSSH (versions before 7.3)
No auth needed
Prerequisites: network access to target SSH server · Python environment with paramiko and Metasploit
devstral-2 · analyzed Jun 12, 2026 Full analysis →
gitlab WORKING POC
by kar0nt3 · poc
https://gitlab.com/kar0nt3/ssh-users-enumeration-by-cve-2016-6210

This script exploits CVE-2016-6210, a timing-based vulnerability in OpenSSH, to enumerate valid usernames by measuring response time differences for existing vs. non-existing users. It uses Paramiko to send crafted authentication attempts and statistical analysis to infer user existence.

Classification
Working Poc 95%
Attack Type
Info Leak
Complexity
Moderate
Reliability
Reliable
Target: OpenSSH (versions affected by CVE-2016-6210)
No auth needed
Prerequisites: network access to the SSH daemon · Python with Paramiko and NumPy libraries
devstral-2 · analyzed Feb 23, 2026 Full analysis →
nomisec WORKING POC
by KiPhuong · poc
https://github.com/KiPhuong/cve-2016-6210

This repository contains functional exploit code for CVE-2016-6210, a timing attack vulnerability in SSH daemons that allows user enumeration. The PoC scripts measure response times for authentication attempts with long passwords to distinguish valid from invalid usernames.

Classification
Working Poc 95%
Attack Type
Info Leak
Complexity
Moderate
Reliability
Reliable
Target: SSH daemons (e.g., OpenSSH)
No auth needed
Prerequisites: Network access to the target SSH daemon · List of potential usernames
devstral-2 · analyzed Feb 18, 2026 Full analysis →
nomisec WORKING POC
by nicoleman0 · poc
https://github.com/nicoleman0/CVE-2016-6210-OpenSSHd-7.2p2

This repository contains a functional exploit for CVE-2016-6210, which leverages timing differences in OpenSSH to enumerate valid usernames. The script uses asynchronous SSH connections and statistical analysis to distinguish between valid and invalid users based on authentication timing.

Classification
Working Poc 95%
Attack Type
Info Leak
Complexity
Moderate
Reliability
Reliable
Target: OpenSSH 7.2p2
No auth needed
Prerequisites: Network access to the target SSH server · List of usernames to test or a single username
devstral-2 · analyzed Feb 18, 2026 Full analysis →
nomisec SCANNER
by coolbabayaga · poc
https://github.com/coolbabayaga/CVE-2016-6210

This repository contains a Python script that performs user name enumeration against SSH daemons affected by CVE-2016-6210 by exploiting a timing side-channel vulnerability. It measures the time taken to respond to authentication attempts with non-existent users versus potential valid users.

Classification
Scanner 100%
Attack Type
Info Leak
Complexity
Moderate
Reliability
Reliable
Target: OpenSSH (versions affected by CVE-2016-6210)
No auth needed
Prerequisites: Network access to the target SSH server · List of potential usernames or a single username to test
devstral-2 · analyzed Feb 18, 2026 Full analysis →

References (12)

Core 12
Core References
Third Party Advisory vendor-advisory
https://security.gentoo.org/glsa/201612-18
Vendor Advisory vendor-advisory
https://access.redhat.com/errata/RHSA-2017:2563
Third Party Advisory, VDB Entry vdb-entry
http://www.securitytracker.com/id/1036319
Mailing List, Third Party Advisory mailing-list
http://seclists.org/fulldisclosure/2016/Jul/51
Third Party Advisory vendor-advisory
http://www.debian.org/security/2016/dsa-3626
Exploit, Third Party Advisory exploit
https://www.exploit-db.com/exploits/40136/
Exploit, Third Party Advisory exploit
https://www.exploit-db.com/exploits/40113/
Release Notes, Vendor Advisory
https://www.openssh.com/txt/release-7.3
Vendor Advisory vendor-advisory
https://access.redhat.com/errata/RHSA-2017:2029
Third Party Advisory, VDB Entry vdb-entry
http://www.securityfocus.com/bid/91812

Scores

CVSS v3 5.9
EPSS 0.8894
EPSS Percentile 99.8%
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

CISA SSVC

Vulnrichment
Exploitation poc
Automatable no
Technical Impact partial

Details

CWE
CWE-200
Status published
Products (1)
openbsd/openssh < 7.2
Published Feb 13, 2017
Tracked Since Feb 18, 2026