Introduction

WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! means your SSH client received a host key for github.com that does not match the key previously saved in your known_hosts file. That can happen after a legitimate host key rotation, but it is also the exact warning SSH uses to protect you against man-in-the-middle attacks, so the first step is verification, not blind deletion.

Why SSH Stops The Connection

SSH stores host keys locally so future connections can prove they are talking to the same server. If the server presents a different key later, SSH assumes something important changed.

For GitHub, the possible explanations are:

• GitHub legitimately rotated or changed host keys
• your known_hosts entry is stale or corrupted
• you are connecting through a proxy, jump host, or interception device
• a real attack is occurring

The security model is working as intended when it refuses to continue automatically.

Verify Before You Remove Anything

Do not immediately trust the new key. First compare the host key or fingerprint with the official GitHub-published SSH key fingerprints.

A normal test command is:

ssh -T [email protected]

If you get the host-identification warning, stop there and verify the key against GitHub’s documentation or official announcement channels.

Remove The Old Stale Entry

Once you have confirmed the change is legitimate, remove the outdated known_hosts entry.

ssh-keygen -R github.com

If your known_hosts file stores entries by IP address or a custom hostname alias, remove that entry instead.

Then reconnect:

ssh -T [email protected]

SSH will present the current key again and ask whether you trust it.

Re-Add The Host Key Safely

Some users prefer to prepopulate known_hosts after verifying the published key.

ssh-keyscan github.com >> ~/.ssh/known_hosts

This is only safe after you verify that the key you are about to trust matches GitHub’s published fingerprints. ssh-keyscan by itself does not authenticate the server.

Why This Happens Specifically With GitHub

GitHub is a high-value service and publishes official SSH fingerprints and guidance because users regularly connect to it over SSH. If GitHub rotates keys, there is usually an official trail showing that the new key is expected.

That is different from a random host change on a private server, where you may need to contact the server owner directly.

Check For Local SSH Config Complications

If the warning persists after removing the entry, inspect your SSH configuration for aliases or alternate hostnames.

ssh -G github.com | grep -E 'hostname|user|identityfile'

You might be connecting to something other than the literal github.com entry you think you are testing.

Common Pitfalls

The most common mistake is deleting the old known_hosts entry without verifying the new fingerprint first. That defeats the whole point of SSH host verification.

Another mistake is removing only github.com while the actual stale record is stored under an IP address, corporate mirror, or SSH alias.

A third issue is assuming the warning is always malicious. It is a security warning, not proof of compromise, but it must be treated cautiously until verified.

Summary

• The warning means the host key presented by GitHub does not match what your SSH client saved earlier.
• Verify the new fingerprint against GitHub’s official SSH fingerprint documentation before trusting it.
• After verification, remove the stale entry with ssh-keygen -R github.com and reconnect.
• 'ssh-keyscan is convenient, but only after you know the fetched key is authentic.'
• Treat this warning as a security check, not as a nuisance to bypass blindly.