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TunnelVision - How Attackers Can Decloak Routing-Based VPNs For a Total VPN Leak (CVE-2024-3661)
(www.leviathansecurity.com)
This is a most excellent place for technology news and articles.
Yeah. Easy to check and get around this. Check your routes before transmitting data, also set up your VPN to push /2s if this relies on /1s, nuke extra routes, etc.
Novel idea though that most people wouldn’t think to look for, but at the end of the day any system will follow its routing table.
I don't think this is a smart way to mitigate this because it could easily result in an arms race. Push /2s, the attacker will switch to /3s; push /4s, the attacker will switch to /5s, etc. Every +1 is going to require doubling the number of routing table entries.
That can't continue forever, obviously, but it's going to result in a negative experience for the user if the VPN client has to push hundreds or thousands of routes to mitigate this attack.