DoS (and possible MITM) in Cisco VPN 3000 Concentrator
TL;DR: the Cisco VPN 3000 Concentrator has a bug that allows you to create a DoS (and maybe a MITM) by sending the wrong netmask in IPSec phase 2. You need valid credentials. Apparently there is no workaround or fix. It’s EOL, so maybe you may want to change it :-)