CVE-2026-44572

Affected scenarios

This affects applications that:

• use middleware or proxy redirects
• are deployed behind a caching CDN or reverse proxy
• allow 3xx responses on those paths to be cached without differentiating internal data requests from normal requests

Workarounds

Before upgrading, users can reduce risk by:

• configuring the CDN or reverse proxy to vary its cache key on x-nextjs-data for affected responses

Next.js uses the x-nextjs-data request header for internal data requests. On affected versions, an external client could send this 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.

CVE-2026-44572 has a CVSS score of 3.7 (Low). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (15.5.16, 16.2.5); upgrading removes the vulnerable code path.

Kodem intelligence

The fix stops trusting x-nextjs-data by itself for middleware redirect handling. A request is now treated as an internal data request only when it is validated as such by internal routing state, preserving legitimate data-request redirect behavior while preventing external header injection from changing normal redirect responses.

1. What is CVE-2026-44572? CVE-2026-44572 is a low-severity security vulnerability in next (npm), affecting versions >= 12.2.0, < 15.5.16. It is fixed in 15.5.16, 16.2.5.
2. How severe is CVE-2026-44572? CVE-2026-44572 has a CVSS score of 3.7 (Low). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of next are affected by CVE-2026-44572? next (npm) versions >= 12.2.0, < 15.5.16 is affected.
4. Is there a fix for CVE-2026-44572? Yes. CVE-2026-44572 is fixed in 15.5.16, 16.2.5. Upgrade to this version or later.
5. Is CVE-2026-44572 exploitable, and should I be worried? Whether CVE-2026-44572 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-44572 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-44572?
   • Upgrade next to 15.5.16 or later
   • Upgrade next to 16.2.5 or later