CVE-2026-44572

A flaw was found in Next.js. An external client could exploit this vulnerability by sending a x-nextjs-data header on a request to a path handled by middleware that returns a redirect. This action could cause the middleware or proxy to incorrectly process the request as a data request, replacing the standard Location redirect header with an internal x-nextjs-redirect header. If the application is deployed behind a caching Content Delivery Network (CDN) or reverse proxy, a malicious request could poison the cached redirect response, leading to a denial of service for subsequent visitors attempting to access the affected path.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

To mitigate this issue, configure any caching Content Delivery Network (CDN) or reverse proxy deployed in front of Next.js applications to either not cache 3xx redirect responses for paths handled by middleware, or to ensure that the cache key for 3xx responses explicitly varies on the x-nextjs-data header. This prevents an attacker from poisoning the cache with an unusable redirect response. Consult your CDN or reverse proxy documentation for specific configuration instructions. A service reload or restart of the CDN/reverse proxy may be required for changes to take effect.