Host and guest suddenly cannot communicate in bridged mode after working fine before

I have the same issue here, and the only solution I could find was to uninstall VirtualBox 5.0.4 r102546 and setup an older version 4.3.30

The only thing else I changed that could have caused the problem was getting the latest windows update (running Windows 7 as host system).

I’ve just spent a while trying to figure this out as well.

Apparently, bridged mode is not working between host and guest in recent releases of VirtualBox 5 according to this ticket (#14457):

In reference to this forum post:

https://forums.virtualbox.org/viewtopic.php?f=6&t=69597

after upgrading to VirtualBox 5.0.x I could no longer ping between the host and the VMs (bridged mode), while the VMs could still ping each other, and all (host and VMs) could still ping other computers on the same subnet. By reverting back to using the NDIS5 driver, all worked properly again, so the issue is related to some bug/defect in the new NDIS6 driver implementation.

At the bottom of this is mention of a test build (#102781) where the issue has been fixed, although I haven’t been able to verify this myself.