This is where having a centralized gem repository might come in handy... If you have 15 projects, you're going to have to go update each and every one.
Usually you do a bundle install when deploying. If you've specified >= 2.2.14 in your Gemfile you just have to redeploy: "cap deploy".
Thanks to user wycats (+team) for bundler. :)
So you still have to redeploy all your 15 projects, as opposed to just fetching the new gem.
You'll also have to do 'bundle update <broken-gem>', commit the resulting Gemfile.lock and hopefully wait for your CI build to pass before deploying. Doing that 15 times would be onerous.