Ok, aqui estava a questão:
Eu estava conectado com a opção ssh -Y
, que ativa trusted X11 forwarding
, conforme descrito em man ssh
:
-Y Enables trusted X11 forwarding. Trusted X11 forwardings are not
subjected to the X11 SECURITY extension controls
(Debian-specific: This option does nothing in the default configuration:
it is equivalent to “ForwardX11Trusted yes”, which is the default as
described above. Set the ForwardX11Trusted option to “no” to restore
the upstream behaviour.This may hange in future depending on client-side
improvements.)
A conexão sem essa opção resolveu de alguma forma.