When I had this problem I discovered that I needed to add these lines to
You should modify the * to some sort of host pattern so it's not enabled for every ssh connection.
You may want to change the ForwardX11Timeout option instead. From
Specify a timeout for untrusted X11 forwarding using the format
described in the TIME FORMATS section of sshd_config(5). X11
connections received by ssh(1) after this time will be refused. The
default is to disable untrusted X11 forwarding after twenty minutes has
If this option is set to “yes”, remote X11 clients will have full
access to the original X11 display.
If this option is set to “no”, remote X11 clients will be considered
untrusted and prevented from stealing or tampering with data belonging
to trusted X11 clients. Furthermore, the xauth(1) token used for the
session will be set to expire after 20 minutes. Remote clients will
be refused access after this time.