CVE-2026-44572
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.
- Score
- CVSS 3.1 5.9 Medium
- Status
- Analyzed - security-advisories@github.com
- Published
- 2026-05-13
- Last modified
- 2026-10-26
- Weaknesses
- CWE-349
Affected products
References
- https://github.com/vercel/next.js/security/advisories/GHSA-3g8h-86w9-wvmq
