Saint Port Shadow, Who Spied in the VPN's Shadow

Patron of VPNs, netfilter tables, and those who think a tunnel is enough to hide.

Life

In 2024 researchers, with Citizen Lab, revealed the port shadow (CVE-2021-3773): by exploiting netfilter's behaviour, an attacker connected to the same VPN server could infer information about another victim's connections, redirect packets, or run classic attacks through the shadow left by the ports. The tunnel meant to protect became a place shared with strangers.

Prayer

O Saint Port Shadow, who spies in the shadow of shared ports, teach our VPNs to isolate users from one another. Amen.

How to celebrate

Celebrated by updating the kernel and choosing VPN configurations that do not leave clients exposed to their tunnel-neighbours.

In the tunnel's shadow the neighbour hides too.