Redis's "Protected Mode" was introduced a couple of years back iirc. It refuses to listen on anything besides localhost if you haven't configured authentication

Redis's "Protected Mode" was introduced a couple of years back iirc. It refuses to listen on anything besides localhost if you haven't configured authentication, unless you explicitly disable the protected mode flag. If you're using the version of redis packaged in trusty/universe, it is extremely old and doesn't contain this. It also contains a handful of critical security vulns that are being openly exploited in the wild. Update manually TODAY.