CVE-2026-44572: Vercel Next.js

Medium severity, CVSS 5.9. EPSS: 0.2% chance of exploitation in the next 30 days.

Next.js is a React framework for building full-stack web applications. From 12.2.0 to before 15.5.16 and 16.2.5, an external client could send a x-nextjs-data header on a normal request to a path handled by middleware that returns a redirect. When that happened, the middleware/proxy could treat the request as a data request and replace the standard Location redirect header with the internal x-nextjs-redirect header. Browsers do not follow x-nextjs-redirect, so the response became an unusable redirect for normal clients. If the application was deployed behind a CDN or reverse proxy that caches 3xx responses without varying on this header, a single attacker request could poison the cached redirect response for the affected path. Subsequent visitors could then receive a cached redirect response without a Location header, causing a denial of service for that redirect path until the cache entry expired or was purged. This vulnerability is fixed in 15.5.16 and 16.2.5.

Affected products

• Vercel Next.js: from 12.2.0, before 15.5.16 (fixed in 15.5.16); from 16.0.0, before 16.2.5 (fixed in 16.2.5)

Published 2026-05-13. Last modified 2026-06-17.