virtualbox.org

I have virtualbox 4.3.26 running on a Windows 7 host with an Ubuntu 14.04 guest. Ever since upgrading virtualbox to the latest version this week, my network interface on the guest (NAT, I've tried all the adapter types available including virtio) disconnects every few minutes and then immediately reconnects. This is annoying as I work primarily in Linux (though I can't run it on my host machine because of company policies).

Dmesg shows this, over and over. Note that I'm currently using the e1000 adapter type, but essentially the same thing happens with all available adapter types:
[ 3847.752236] e1000: eth0 NIC Link is Down
[ 3847.752363] e1000 0000:00:03.0 eth0: Reset adapter
[ 3852.207690] IPv6: ADDRCONF(NETDEV_UP): eth0: link is not ready
[ 3853.816533] e1000: eth0 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: RX
[ 3853.816853] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
[ 4328.768220] e1000: eth0 NIC Link is Down
[ 4332.776535] e1000: eth0 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: RX
[ 4509.128250] e1000: eth0 NIC Link is Down
[ 4513.136564] e1000: eth0 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: RX
[ 5408.960262] e1000: eth0 NIC Link is Down

My machine is connected by a single ethernet cable and I have noticed no network issues on the host at all. Wifi is completely disabled. I'm at a loss. Does anyone know what might be causing this?

Did you also update the guest additions to 4.3.26?

Yes, I updated the guest additions immediately after upgrading virtualbox.

There have been a few still having this issue and you need to add your information to the bug ticket
https://www.virtualbox.org/ticket/13839

update the to 4.3.27 works ok for me