CVE-2026-44575: Next.js: Middleware / Proxy bypass in App Router applications via segment-prefetch routes
Impact
App Router applications that rely on middleware or proxy-based checks for authorization can allow unauthorized access through transport-specific route variants used for segment prefetching. In affected configurations, specially crafted .rsc and segment-prefetch URLs can resolve to the same page without being matched by the intended middleware rule, which can allow protected content to be reached without the expected authorization check.
Fix
We now include App Router transport variants when generating middleware matchers, so middleware protections are applied consistently to those requests as well as to the normal page URL.
Workarounds
If you cannot upgrade immediately, enforce authorization in the underlying route or page logic instead of relying solely on middleware.
Other sources
Next.js is a React framework for building full-stack web applications. From 15.2.0 to before 15.5.16 and 16.2.5, App Router applications that rely on middleware or proxy-based checks for authorization can allow unauthorized access through transport-specific route variants used for segment prefetching. In affected configurations, specially crafted .rsc and segment-prefetch URLs can resolve to the same page without being matched by the intended middleware rule, which can allow protected content to be reached without the expected authorization check. This vulnerability is fixed in 15.5.16 and 16.2.5.
— MITRE
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
npm/nextto a version that resolves this vulnerability.Fixed in 16.2.5 - Upgrade
Upgrade
npm/nextto a version that resolves this vulnerability.Fixed in 15.5.16 - Upgrade
Upgrade
Next.jsto a version that resolves this vulnerability.Fixed in 15.5.16 - Upgrade
Upgrade
Next.jsto a version that resolves this vulnerability.Fixed in 16.2.5 - Configuration
If you cannot upgrade, enforce authorization in the underlying route or page logic instead of relying solely on middleware (middleware/proxy-based checks may be bypassed via transport-specific App Router segment-prefetch route variants).
Next.js App Router authorization flow middleware-only authorization = disallow
Event History
Frequently Asked Questions
What is the severity of CVE-2026-44575?
CVE-2026-44575 has been classified with a serious severity level that could result in unauthorized access through middleware or proxy bypass.
How do I fix CVE-2026-44575?
To fix CVE-2026-44575, update your Next.js application to version 15.5.16 or 16.2.5.
What versions of Next.js are affected by CVE-2026-44575?
CVE-2026-44575 affects Next.js versions from 15.2.0 to 15.5.16 and from 16.0.0 to 16.2.5.
Who is impacted by CVE-2026-44575?
Developers using Next.js with middleware or proxy checks for authorization are impacted by CVE-2026-44575.
What type of vulnerability is CVE-2026-44575?
CVE-2026-44575 is a middleware and proxy bypass vulnerability in Next.js applications.