In quite a few environments I see Cisco hardware treated as 'set it and forget it'. Many admins just don't even think about updating IOS. If you look in places like Packstorm or Bugtraq, some months you will see tons of attacks all centered at IOS. What are the real risks being taken if someone does not have an interest in keeping their routers/switches up to date especially when a new zero day gets launched?
Update: We are all smart and know what theoretical problems can be caused, but it has been my experience that these networks are left standing for quite sometime, even though an internal employee could leverage this if they so wished.
Has anyone experienced an attack on Cisco gear that would like to chime in?