VirtualBox has a long standing issue about IPv6 connectivity over a bridged wireless adapter.
The current and easiest workaround I've found is to remove the neighbor entry corresponding to the IPv6 router in the neighbor table. This is on in Linux guest on a Windows host.
$ ping6 icanhazip.com
PING icanhazip.com(2606:4700::6812:7361) 56 data bytes
^C
--- icanhazip.com ping statistics ---
5 packets transmitted, 0 received, 100% packet loss, time 0ms
rtt min/avg/max/mdev = 0.000/0.000/0.000/0.000 ms
$ ip -6 neigh
2001:db8:1::1 dev enp0s3 lladdr 00:11:95:ad:be:ef router STALE
2001:db8:1:211:95ff:dead:beef dev enp0s3 FAILED
fe80::211:95ff:dead:beef dev enp0s3 router FAILED
$ sudo ip -6 neigh del fe80::211:95ff:dead:beef dev enp0s3
$ ping6 -c 3 icanhazip.com
PING icanhazip.com(2606:4700::6812:7361) 56 data bytes
64 bytes from 2606:4700::6812:7361: icmp_seq=1 ttl=51 time=202 ms
64 bytes from 2606:4700::6812:7361: icmp_seq=2 ttl=51 time=213 ms
64 bytes from 2606:4700::6812:7361: icmp_seq=3 ttl=51 time=118 ms
--- icanhazip.com ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2004ms
rtt min/avg/max/mdev = 118.575/178.169/213.682/42.400 ms
The neighbor entry will become STALE again after every 30 seconds and will eventually expire and won't work anymore after some time. An option is to create a cron job that runs every 2 minutes and deletes the table entry.
*/2 * * * * ip -6 neigh | while read line; do set -- $line; ip neigh del $1 dev $3; done; ping6 -n -c 2 $ipv6_gw &>/dev/null
where $ipv6_gw is the address of the local IPv6 gateway to the Internet.
Original VBox ticket is now closed. However the issue (if it still exists) could still be related to https://www.virtualbox.org/ticket/14212.
Also, I'm not sure if this is related in any way, but if I start docker containers in the Linux VM (I'm now on a Win11 host), the containers can't reach the IPv6 internet, even though the same docker setup works on other non-VM Linux systems (globally routable IPv6 addresses; not using docker6-ipv6nat here and not in favor of using it). (Details: a Wireshark trace running on the Win11 host shows that Neighbor Discovery Solicitations are sent out, but ND Advertisements never reach the VM although I see them come in on the host.)