I would like to know if there is any "advertising platform" cms arround, in order to host affiliate marketing tags / banners / etc
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Open-source "ad server solution" Open X is incredibly powerful, but might have a bit too much of a learning curve if all you're looking to do is affiliate banners.
As an out-of-the-box suggestion, Kajabi is a hosted service. I haven't used it, but it looks like it could be worth a look if it fits your product and business model. Otherwise, you could use a CMS like Joomla or Wordpress and integrate with an affiliate service. Zferral and HasOffers are two such affiliate services you could use. Personally, I recommend the second method.
I would recommend finding a third party module and using one of the mainstream CMS platforms out there, such as Drupal, Jooma & Wordpress. You can in addition integrate Google Ads if that is needed.
is a CMS really necessary for that? Most affiliate systems have this functionality built in. In a custom coded (asp, php, rails, ) solution this would be very easy to setup and manage.