No /etc/memcached.conf:
# Specify which IP address to listen on. The default is to listen on all IP addresses
# This parameter is one of the only security measures that memcached has, so make sure
# it's listening on a firewalled interface.
-l 127.0.0.1
Altere isso para
-l 0.0.0.0
e reinicie o memcached.