Tools

Serv-U users are not able to connect using FileZilla version 3.70.0

Users may experience connection issues when attempting to access Serv-U using FileZilla version 3.70.0.

First published date

4/13/2026 1:08 PM

Last published date

4/22/2026 5:10 PM

Overview

Connection attempts made using FileZilla version 3.70.0 are unsuccessful when connecting to Serv-U. The issue appears to occur on the FTP client side, and no related entries are recorded in the Serv-U logs during these attempts.

Earlier versions of FileZilla (such as 3.69.1 and 3.69.6) can connect successfully to the same Serv-U environment without any issues.

Product section

Serv-U Managed File Transfer & Serv-U FTP Server

Cause

The issue appears to be related to a change introduced in FileZilla version 3.70.0. Since the problem does not occur with earlier versions and no logs are generated on the Serv-U side, the behavior is believed to originate from the FTP client.

Additionally, this behavior has been observed on both Windows and Linux environments running Serv-U, with different outcomes:

Windows Server (e.g., Windows Server 2016): Connection attempts fail, and users are unable to connect.
Linux OS: The Serv-U service may crash when connection attempts are made using FileZilla version 3.70.0.

Resolution

Filezilla released version 3.70.4 on April 21, 2026, and it has been confirmed to work with Serv-U.
Upgrade to this version.

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