Next.js middleware lacks a built-in mechanism for passing values across different parts of an application, but it offers a feature called "rewrites" that can be utilized to modify request metadata and pass data. This involves rewriting requests to the same URL while incorporating desired data into the request's metadata, which can then be accessed via API routes or getServerSideProps. However, inconsistencies across different runtimes can pose challenges in implementing this process. The provided code snippets offer solutions to mitigate these issues, using functions to set and retrieve context data securely while preventing spoofing through pre-defined keys. Limitations include the need for all key/value pairs to be strings due to restrictions in headers and query strings, and potential constraints on the total length of these elements by hosting providers like Vercel.