Next.js HTTP Request Smuggling Issues

Next.js is a React framework for building full-stack web applications. From versions 15.0.4-canary.51 to before 15.1.8, a cache poisoning bug leading to a Denial of Service (DoS) condition was found in Next.js. This issue does not impact customers hosted on Vercel. Under certain conditions, this issue may allow a HTTP 204 response to be cached for static pages, leading to the 204 response being served to all users attempting to access the page. This issue has been addressed in version 15.1.8.

Next.js is a React framework for building full-stack web applications. In Next.js App Router from 15.3.0 to before 15.3.3 and Vercel CLI from 41.4.1 to 42.2.0, a cache poisoning vulnerability was found. The issue allowed page requests for HTML content to return a React Server Component (RSC) payload instead under certain conditions. When deployed to Vercel, this would only impact the browser cache, and would not lead to the CDN being poisoned. When self-hosted and deployed externally, this could lead to cache poisoning if the CDN does not properly distinguish between RSC / HTML in the cache keys. This issue has been resolved in Next.js 15.3.3.