I'd like to start by saying that I've searched for hours and could not find a definitive answer to my question.

Across different sites on different second-level domains exists a universal navigation bar with a collection of roughly 30 links. This universal bar is exactly the same for every page on each domain. The bar's HTML, CSS and JavaScript are all stored in a subfolder for each domain and the HTML is embedded upon serving the page and is not being injected on the client side. None of the links use any rel directives and are as vanilla as can be.

My question is about Google's duplicate content rule. Would something like this be considered duplicate content? Matt Cutt's blog post about duplicate content mentions boilerplate repetition, but then he mentions lengthy legalese. Since the text in this universal bar is brief and uses common terms, I wonder if this same rule applies.

If this is considered duplicate content, what would be a good way to correct the problem?

Thank you for your help.