Pulling this off requires high privileges in the network, so if this is done by intruder you’re probably having a Really Bad Day anyway, but might be good to know if you’re connecting to untrusted networks (public wifi etc). For now, if you need to be sure, either tether to Android - since the Android stack doesn’t implement DHCP option 121 or run VPN in VM that isn’t bridged.
The title is misleading in that the attack isn’t against the VPN apps or even the VPN protocols, but against the networking stack of the operating system.
I also don’t get much value out of the statement that “every” OS except Android is vulnerable. Do they really mean all other OSes, or just what would come to mind for most people, i.e. Windows, macOS, Linux, iOS? What about the various BSDs for example?
It’s a DHCP manipulation attack, so every RFC 3442 compliant DHCP implementation implementing option 121 would be “vulnerable” (it’s not vulnerability though). Android apparently doesn’t implement it, so it’s technically impossible to pull off against Android device. There might be others, but I’d guess most serious server/desktop OS’es implement it.
The title isn’t misleading at all, even though the “neutering their entire purpose” is a bit of a click-bait. This doesn’t affect ingress VPN at all.
It’s an attack that uses DHCP features (according to RFC).
It’s a clever way to uncloak egress VPN users, therefore it does have privacy impact since most of us use VPN for purposes of hiding out traffic from the local network and provider and there’s no “easy” fix since it’s just a clever use of existing RFC.
Slightly off topic, but it turns out Android has a different VPN vulnerability:
https://mullvad.net/en/blog/dns-traffic-can-leak-outside-the-vpn-tunnel-on-android
Only if you dont have tunnel dns configured