To fix this you must either remove write permissions on the users root directory with the following command, replacing the directory with your users root:

chmod a-w /home/user

Or you can work around this security check by adding either of the two below into your configuration file.

For the standard vsFTPd build (vsftpd):

allow_writeable_chroot=YES

For the extended vsFTPd build (vsftpd-ext):

allow_writable_chroot=YES

Removing the write permission on the root isn’t a perfect solution as doing this can cause a few problems with things that need to write to the root directory, such as the bash history file or some graphical environments.