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“Host key verification failed” means SSH received a server identity that does not match the one it previously recorded for that host. The change may be legitimate, but it could also mean you are connecting to the wrong server or that the connection is being intercepted. Confirm the expected fingerprint with the server administrator or the provider’s official documentation before changing known_hosts or accepting a new key. If you cannot verify the identity, do not connect.
What the SSH error means
On an SSH connection, the server presents a host key to identify itself. Your SSH client checks that key against the identity it previously saved for the host. If the keys do not match, SSH stops the connection with this warning as a security precaution. Git and other applications can show the same error when they use SSH to connect.
A mismatch alone does not explain why the key changed. The server may have been rebuilt or its SSH keys rotated, or the connection may be reaching a different endpoint. Only the server owner or a trusted official source can confirm which key is expected. GitHub’s guidance on this error likewise advises checking for an official explanation and not connecting if you cannot find a trustworthy source for the key.
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Host-key verification is about the server’s identity, not your user credentials. Verifying the server does not itself authenticate you to a Git account or grant repository access.
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How to check the warning before changing anything
- Read the complete warning. Note the hostname, port if shown, key algorithm, presented fingerprint, and any line pointing to an offending record in
known_hosts. The fingerprint is the value you need to compare with a trusted source. - Confirm the intended endpoint. Check the hostname and port in the command or application configuration. If you used a short alias, review the SSH configuration that maps it to a hostname, port, or other connection settings.
- Find the expected fingerprint through an authoritative channel. Ask the server administrator or consult the provider’s official key page or change announcement. Do not rely on an unverified message or on a fingerprint copied from an unrelated host.
- Compare the details. The hostname and port must refer to the intended server, and the presented key’s algorithm and fingerprint must agree with the authoritative information. A notice that a key changed is useful only if it comes from a source responsible for that server.
- Stop if you cannot confirm the match. Contact the organization that operates the server rather than deleting the record or bypassing the check.
For GitHub: compare against its official fingerprints
If the intended endpoint is GitHub, compare the fingerprint in the warning with GitHub’s current SSH key fingerprints. GitHub publishes fingerprints for its RSA, ECDSA, Ed25519, and DSA host keys. The values can change, so use the official page for the comparison rather than treating a copied value as permanent. GitHub labels its DSA fingerprint “closing down.”
GitHub’s post about its RSA host-key update documents a real key rotation and uses ssh-keygen -R github.com to remove the previous record. That is an example of a confirmed provider change, not proof that a warning for another hostname—or an unexplained warning for GitHub—is safe to ignore. See GitHub’s RSA SSH host-key update announcement.
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How to update the saved key after verifying it
Proceed only after the administrator or provider confirms that the fingerprint presented by the intended endpoint is valid. Remove or replace only the record for that host; do not clear all saved host keys or disable host checking.
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- Identify the affected host record. Use the hostname and port from the warning, and check which user or system
known_hostsfile SSH is using if the warning identifies a file and line. - Remove the stale record or replace it with the verified one. For GitHub, its documented RSA-rotation example uses
ssh-keygen -R github.com. For other hosts, use the exact host or host-and-port entry reported by SSH; do not substitute the GitHub example. - Reconnect to the same endpoint. When prompted, compare the newly presented fingerprint with the authoritative value again. Accept the key only if it matches.
If the warning continues after the key is confirmed
- A different host or port is being used. Check the command, application settings, SSH aliases, and custom port configuration against the administrator’s intended endpoint.
- SSH is reading another host-key file. A different user account or system-level SSH configuration may point to a separate
known_hostsfile. Check the file named in the warning and ask the administrator which configuration applies. - The server has multiple legitimate keys. Compare the algorithm and fingerprint for the specific key shown in the warning with the provider’s published fingerprints or the administrator’s confirmation.
- The endpoint or key still cannot be confirmed. Stop and contact the server owner. Do not turn off host-key verification to make the connection succeed.
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