Issue Remote FTP Backup fails

[EnriqueR]

Server operating system version

Ubuntu 24.04.2 LTS

Plesk version and microupdate number

18.0.68

Since the last update, the Backup manager via FTP remote storage configuration no longer works for me. It returns the following error message. I have checked the FTP server and it is OK. I am sure of this because I have 3 additional Plesk servers using the same type of backup and they can access it without any problem. The only one that is giving access problems is the one I have updated to the latest version 18.0.68.

 

[Bitpalast]

What is the error message?

 

[EnriqueR]

Error: No ha sido posible cargar el archivo al almacenamiento: Stream error: /check0/test: Curl error: Unable to finish an upload: (18) Transferred a partial file: The last FTP request: STOR test: The last FTP response: 522 Unable to secure data connection: Connection to the FTP server has lost
Compruebe que dispone de permisos para cargar archivos al almacenamiento. Puede comprobarlo de forma independiente con los siguientes comandos:
echo 123 | curl -T - --ftp-create-dirs -v --ftp-pasv --ssl -k -u ftp_plesk 'ftp://ftpserver.com/test-dir/test-file.txt'
curl -v --ftp-pasv --ssl -k -u ftp_plesk 'ftp://ftpserver.com/test-dir/'

The strange thing is that using the specified command,

echo 123 | curl -T - --ftp-create-dirs -v --ftp-pasv --ssl -k -u ftp_plesk 'ftp://ftpserver.com/test-dir/test-file.txt'

it works correctly. Also, checking in the logs of the FTP server, the connection and access test performed from Plesk is done without problems.
It only fails in the Plesk panel. It is very strange.

 

[Bitpalast]

Does this also occur when you disable the FTPS option in the backup settings?

 

[EnriqueR]

The FTP server always forced a secure connection. I followed your test request and disabled this limitation in FTP server.
Now it works correctly with the FTPS option enabled/disabled in Plesk backup system.

It is very rare that now it fails for that reason and in previous Plesk versions it works correctly.

 

[Bitpalast]

I believe this should be examined in detail by Plesk support, because it could be a bug with SSL versions or cipher lengths. In such cases, it is always helpful to submit a ticket to Plesk support.

https://support.plesk.com/hc/en-us/articles/12388090147095-How-to-get-support-directly-from-Plesk