I've got a client where an internal scan said one of their core routers has a RIP-2 Poisoning issue.

This is the exact Nessus description:
Tenable Network Security

I understand that an attacker could create bogus routes, but what's the worst case scenario?
Any traffic on the LAN isn't going to be routed anyway, so any LAN traffic should be effected by this right?
You could do a man in the middle with WAN traffic, you could intercept emails. Anything else?