GitHub SSH Connections Show “Warning: Remote Host Identification Has Changed”

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If you’re a developer using GitHub, you’ve probably encountered the dreaded error message:

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@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @
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IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!

This error can stop your Git push or pull in its tracks, leaving you wondering what went wrong. Don’t panic! In this comprehensive guide, we’ll explain why the “Warning: Remote Host Identification Has Changed” error happens when connecting to GitHub over SSH, how to fix it, and how to prevent it in 2025. Whether you’re on Windows, macOS, or Linux, we’ve got you covered with simple, step-by-step solutions. Let’s dive in!

What Does the “Warning: Remote Host Identification Has Changed” Error Mean?

The error pops up when your computer’s SSH client detects a mismatch between the GitHub server’s current SSH host key and the one stored in your local known_hosts file. Think of it as your computer saying, “Hey, this server doesn’t look like the GitHub I know. Something’s different!”

SSH (Secure Shell) is a secure way to connect to remote servers like GitHub. It uses a “fingerprint” (a unique host key) to verify the server’s identity. Your computer saves this fingerprint in the ~/.ssh/known_hosts file the first time you connect. If the server’s key changes later, SSH throws the warning to protect you from potential security risks, like a man-in-the-middle attack.

Why Is This Warning Important?

This error is a security feature, not a bug. It alerts you to possible issues, such as:

  • A legitimate change in GitHub’s SSH host key.
  • A network issue or server misconfiguration.
  • A rare but serious security threat, like someone trying to impersonate GitHub.

In 2023, many GitHub users saw this error because GitHub updated its RSA SSH host key after a security incident. While such events are rare, they highlight why this warning exists.

Why Does This Error Happen with GitHub SSH Connections?

There are several reasons why you might see the “Warning: Remote Host Identification Has Changed” error when connecting to GitHub. Let’s break them down:

1. GitHub Updated Its SSH Host Key

The most common cause is GitHub updating its RSA SSH host key. For example, on March 24, 2023, GitHub replaced its RSA key after it was briefly exposed in a public repository. This change caused the error for users whose known_hosts file still had the old key.

  • Why does this happen? GitHub periodically updates its keys for security, which changes the server’s fingerprint.
  • How often? Rarely, but it’s a standard practice when a key is compromised or as a precaution.

2. IP Address or Hostname Changes

GitHub’s servers use multiple IP addresses, and these can change for security or infrastructure reasons. If your known_hosts file references an old IP address for github.com, a new connection to a different IP might trigger the warning.

3. Local known_hosts File Issues

Your known_hosts file might have outdated or conflicting entries. For example:

  • You connected to GitHub before, and the old key is still stored.
  • Multiple entries for github.com or its IPs cause confusion.

4. Network or DNS Issues

Sometimes, network configurations or DNS problems can make it seem like you’re connecting to a different server. This might happen if:

  • Your ISP or network redirects traffic incorrectly.
  • A corporate firewall or VPN interferes with the connection.

5. Potential Security Threats

While rare, the error could indicate a man-in-the-middle attack, where someone is trying to intercept your connection. SSH’s warning is designed to catch this. Always verify the server’s authenticity before proceeding.

How to Fix the “Warning: Remote Host Identification Has Changed” Error

Before fixing the error, ensure it’s safe to proceed. If you’re confident the issue is due to a legitimate change (e.g., GitHub’s key update), follow these steps. We’ll cover solutions for Windows, macOS, and Linux.

Step 1: Verify GitHub’s SSH Key

To rule out a security threat, check GitHub’s official SSH key fingerprints. GitHub publishes these on its documentation page. As of 2025, the RSA key fingerprint is:

SHA256:uNiVztksCsDhcc0u9e8BujQXVUpKZIDTMczCvj3tD2s

Compare this with the fingerprint in the error message. If they match, it’s safe to proceed. You can also verify keys via GitHub’s API or blog posts.

Step 2: Remove the Old Key from known_hosts

The simplest fix is to remove the outdated GitHub entry from your known_hosts file. Here’s how:

On macOS or Linux

  1. Open a terminal.
  2. Run the following command to remove GitHub’s old key:
   ssh-keygen -R github.com

This removes all entries for github.com from ~/.ssh/known_hosts.

  1. If the error references a specific IP (e.g., 140.82.121.4), remove that too:
   ssh-keygen -R 140.82.121.4
  1. Try connecting again (e.g., git push or ssh -T git@github.com). You’ll be prompted to accept the new key:
   The authenticity of host 'github.com' can't be established.
   RSA key fingerprint is SHA256:uNiVztksCsDhcc0u9e8BujQXVUpKZIDTMczCvj3tD2s.
   Are you sure you want to continue connecting (yes/no)? yes

Type yes to add the new key to known_hosts.

On Windows

Windows users might use Git Bash, PowerShell, or PuTTY. Here’s how to fix it:

Using Git Bash or PowerShell
  1. Open Git Bash or PowerShell.
  2. Run the same command as for macOS/Linux:
   ssh-keygen -R github.com
  1. If needed, remove specific IPs (e.g., ssh-keygen -R 140.82.121.4).
  2. Reconnect to GitHub and accept the new key when prompted.
Using PuTTY
  1. Open PuTTY.
  2. Go to Configuration > Connection > SSH > Host Keys.
  3. Find and delete the entry for github.com.
  4. Save changes and reconnect. PuTTY will prompt you to accept the new key.
Manual Edit (Alternative)

If the above doesn’t work:

  1. Open the known_hosts file in a text editor. It’s usually at:
  • C:\Users\<YourUsername>\.ssh\known_hosts (Windows)
  • ~/.ssh/known_hosts (macOS/Linux)
  1. Find the line starting with github.com or the IP in the error (e.g., 140.82.121.4).
  2. Delete that line and save the file.
  3. Reconnect to GitHub to add the new key.

Step 3: Update the known_hosts File with the New Key

Instead of waiting for the prompt, you can manually add GitHub’s new key:

  1. Run:
   ssh-keyscan github.com >> ~/.ssh/known_hosts

This appends GitHub’s current key to your known_hosts file.

  1. Verify the key matches GitHub’s official fingerprint.

Step 4: Test the Connection

Test your SSH connection to GitHub:

ssh -T git@github.com

If successful, you’ll see a message like:

Hi <username>! You've successfully authenticated...

Advanced Fixes for Persistent Issues

If the error persists, try these troubleshooting steps:

1. Clear All known_hosts Entries (Use with Caution)

Delete the entire known_hosts file:

rm ~/.ssh/known_hosts

This removes all stored keys, so you’ll need to re-verify every SSH server you connect to. Avoid this if you have multiple servers or automated scripts.

2. Check for IP-Specific Errors

If the error mentions an IP (e.g., 140.82.121.4), it might be due to GitHub’s IP rotation. Remove all GitHub-related IPs:

ssh-keygen -R 140.82.121.4
ssh-keygen -R 192.30.255.113

Then reconnect to update the keys.

3. Update SSH Client

An outdated SSH client might cause issues. Update OpenSSH:

  • macOS/Linux: sudo apt update && sudo apt install openssh-client (Ubuntu) or brew install openssh (macOS with Homebrew).
  • Windows: Update Git for Windows or OpenSSH via PowerShell.

4. Check Network or VPN Settings

If you’re on a corporate network or VPN, it might redirect traffic. Try:

  • Switching to a different network.
  • Disabling the VPN temporarily.
  • Contacting your network admin to check for DNS issues.

5. Disable Strict Host Key Checking (Not Recommended)

As a last resort, you can bypass the check by editing your SSH config (~/.ssh/config):

Host github.com
  StrictHostKeyChecking no
  UserKnownHostsFile=/dev/null

Warning: This reduces security and should only be used temporarily for testing.

Preventing the Error in 2025

To avoid this error in the future, follow these best practices:

1. Stay Informed About GitHub Updates

GitHub announces key changes on its blog or X. Follow @github on X or check the GitHub Blog for updates.

2. Regularly Update known_hosts

Periodically clear old GitHub entries:

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

3. Enable Two-Factor Authentication (2FA)

2FA adds an extra layer of security to your GitHub account, reducing risks if a key is compromised.

4. Backup Your known_hosts File

Before making changes, back up your known_hosts file:

cp ~/.ssh/known_hosts ~/.ssh/known_hosts.bak

5. Use HTTPS Instead of SSH

If SSH issues persist, consider using HTTPS for Git operations. It’s less prone to key-related errors but requires a personal access token.

FAQs About GitHub SSH “Warning: Remote Host Identification Has Changed”

Why did GitHub change its SSH key in 2023?

GitHub updated its RSA SSH key on March 24, 2023, after the private key was briefly exposed in a public repository. This was a precautionary measure to ensure security.

Is this error a sign of a hack?

Not usually. It’s often due to a legitimate key change or network issue. Always verify the server’s fingerprint before proceeding.

Can I ignore the warning?

No, don’t ignore it. Verify the key and update your known_hosts file to stay secure.

What if I use ECDSA or Ed25519 keys?

GitHub’s 2023 update only affected RSA keys. ECDSA and Ed25519 users didn’t need to take action.

How do I find my known_hosts file?

It’s typically at ~/.ssh/known_hosts on macOS/Linux or C:\Users\<YourUsername>\.ssh\known_hosts on Windows.

Conclusion: Keep Your GitHub SSH Connections Smooth in 2025

The “Warning: Remote Host Identification Has Changed” error might look scary, but it’s usually a simple fix. By understanding why it happens—whether it’s a GitHub key update, IP change, or local issue—you can resolve it quickly and securely. Always verify the server’s fingerprint, update your known_hosts file, and stay informed about GitHub’s security updates.

With the steps in this guide, you’ll be back to pushing and pulling code in no time. Have you run into this error before? Let us know your experience or any tips in the comments below! Happy coding!

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