Are you getting Host key verification failed sftp error?

Often, the users may get this error while attempting to connect using SFTP to the host server.

Unfortunately, the error occurs due to the mismatch of the private key from the list of known hosts files, which contains the host key.

At Bobcares, we often get requests from our customers to fix an error message Host key verification failed sftp as part of our Server Management Services.

Today, let’s get into the details on how our Support Engineers fix this error.

What is Host key verification failed sftp error?

SFTP is a secure version of the File Transfer Protocol, which facilitates data access and transfer over a Secure Shell (SSH) data stream.

By default, it uses the unique host key for verifying the exact server. This error occurs due to the mismatch of key verified from the ~/.ssh/known_hosts file.

While trying to connect the host server via sftp protocol, the user may get the following.

Initially, when the customer connects to a server via SSH, the public host key of the client has been saved to the ~/.ssh/known_hosts file.

The next time when users connect to the remote server, the client compares this key to the one that the server supplies.

After that, a connection will establish when the key matches, otherwise the Host key verification failed sftp error will pop up.

How to fix Host key verification failed sftp

Usually, our Support Engineers fix the error by removing the old key from the ~/.ssh/known_hosts file. Removal of the old key is either done manually or by using the ssh-keygen command.

1. Manual removal of key

One of our customers approached us with a problem with file transfer. He received an error when he tried to upload a file via SFTP to another system.

The error said Host key verification failed sftp.

Normally, all the keys are available in the file ~/. ssh/known_hosts. The file known_hosts will be found in the home directory of its user. This error happens due to a mismatch of the private key from the list of known hosts files.

The fix involves the manual removal of the offending key from the file.

To fix the error, we opened the ~/.ssh/known_hosts file and removed the entry from the known_hosts file.

Thus, it resolved the problem of the customer and he could upload files via sftp.

2. ssh-keygen command

Similarly, when a key mismatch occurs, we use the ssh-keygen command to remove the old key from the file ~/.ssh/known_hosts.

ssh-keygen -R [hostname|IP address]

After the removal of the key by using any of this method, the remote server asks for a confirmation to add the new key to the ~/.ssh/known_host file. It indicates the successful removal of the old key.

3. Problem with root user’s key

Often, many customers find problems while transferring files from one server to another. They may have the following error when they try to transfer the file.

"Could not open location 'sftp://dad@192.168.0.3/home/dad/Desktop/Desktop-Laptop%20swap%20file' Host key verification failed"

Sometimes, this occurs when the root user’s key mismatch with the key that already stored in the known_host file. Then we have to remove the old key entry from /root/.ssh/known_hosts file.

So our Support Engineers removed the old key by using the ssh-keygen command. After that, the user was easily able to transfer the files without any error.

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Conclusion

In short, Host key verification failed sftp error mainly occurs when the server’s public host key mismatches with the key in the known_hosts file. Today, we saw how our Support Engineers fix this error for our customers.