The Open Connectivity Foundation UPnP specification before 2020-04-17 does not forbid the acceptance of a subscription request with a delivery URL on a different network segment than the fully qualified event-subscription URL, aka the CallStranger issue.
{ "availability": "Available with Ubuntu Pro (Infra-only): https://ubuntu.com/pro", "ubuntu_priority": "medium", "binaries": [ { "hostapd-dbgsym": "1:2.1-0ubuntu1.7+esm3", "wpasupplicant-udeb": "2.1-0ubuntu1.7+esm3", "wpagui-dbgsym": "2.1-0ubuntu1.7+esm3", "hostapd": "1:2.1-0ubuntu1.7+esm3", "wpagui": "2.1-0ubuntu1.7+esm3", "wpasupplicant": "2.1-0ubuntu1.7+esm3", "wpasupplicant-udeb-dbgsym": "2.1-0ubuntu1.7+esm3", "wpasupplicant-dbgsym": "2.1-0ubuntu1.7+esm3" } ] }
{ "availability": "No subscription required", "ubuntu_priority": "medium", "binaries": [ { "hostapd-dbgsym": "1:2.4-0ubuntu6.7", "wpasupplicant-udeb": "2.4-0ubuntu6.7", "wpagui-dbgsym": "2.4-0ubuntu6.7", "hostapd": "1:2.4-0ubuntu6.7", "wpagui": "2.4-0ubuntu6.7", "wpasupplicant": "2.4-0ubuntu6.7", "wpasupplicant-udeb-dbgsym": "2.4-0ubuntu6.7", "wpasupplicant-dbgsym": "2.4-0ubuntu6.7" } ] }
{ "availability": "No subscription required", "ubuntu_priority": "medium", "binaries": [ { "hostapd-dbgsym": "2:2.6-15ubuntu2.7", "wpasupplicant-udeb": "2:2.6-15ubuntu2.7", "wpagui-dbgsym": "2:2.6-15ubuntu2.7", "hostapd": "2:2.6-15ubuntu2.7", "wpagui": "2:2.6-15ubuntu2.7", "wpasupplicant": "2:2.6-15ubuntu2.7", "wpasupplicant-dbgsym": "2:2.6-15ubuntu2.7" } ] }
{ "availability": "No subscription required", "ubuntu_priority": "medium", "binaries": [ { "gir1.2-gupnp-1.2": "1.2.3-0ubuntu0.20.04.1", "libgupnp-1.2-0-dbgsym": "1.2.3-0ubuntu0.20.04.1", "libgupnp-1.2-dev": "1.2.3-0ubuntu0.20.04.1", "libgupnp-1.2-0": "1.2.3-0ubuntu0.20.04.1", "libgupnp-doc": "1.2.3-0ubuntu0.20.04.1" } ] }
{ "availability": "No subscription required", "ubuntu_priority": "medium", "binaries": [ { "hostapd-dbgsym": "2:2.9-1ubuntu4.2", "wpasupplicant-udeb": "2:2.9-1ubuntu4.2", "wpagui-dbgsym": "2:2.9-1ubuntu4.2", "hostapd": "2:2.9-1ubuntu4.2", "wpagui": "2:2.9-1ubuntu4.2", "wpasupplicant": "2:2.9-1ubuntu4.2", "wpasupplicant-dbgsym": "2:2.9-1ubuntu4.2" } ] }