How to fix MetaDefender Client "Fatal Error!" with MetaDefender Core over HTTPS?

If MetaDefender Core has been configured to run over HTTPS with a self-signed certificate, you may receive a fatal error message when connecting MetaDefender Client to the MetaDefender Core server. This error is caused by an incorrectly created certificate.


To fix this, ensure that the Common Name set during certificate creation matches the HostName/ServerName of the MetaDefender Core machine.

For example, if the MetaDefender Core machine's hostname is "Server1" and you input "Server2" as the Common Name when creating the SSL, you will receive an error with the notification that the certificate's address is mismatched.


After the certificate is created, run the MetaDefender Client and specify the hostname and port of the MetaDefender Core machine (e.g. https://server2:8008/).

This will NOT work if the value is the IP of the MetaDefender Core machine (e.g.

Note: Even though the MetaDefender Core is configured to run over HTTPS, the port used will remain on 8008 (see above URL examples). If port 443 is desired, Metadefender Core must be configured to run on this port (443), instead of 8008.

To change the port of a MetaDefender Core instance:

  1. Navigate to the registry editor.


  3. Change the value of the restport key.

After the value has been changed, ometascan and ometascan-node services must be restarted. Input the new URL when prompted by the Client (e.g. https://server2:443).


For information on how to configure MetaDefender Core to run over HTTPS, please see our documentation:

This article pertains to MetaDefender Client 4.0.1. and above
This article was last updated on 2019-10-24.