CVE-2026-44574: Authorization Bypass in Next.js

The primary impact of CVE-2026-44574 is unauthorized access to protected resources within a Next.js application. Attackers can craft malicious query parameters that alter the dynamic route value seen by the application's pages, effectively bypassing middleware checks designed to enforce access control. This could lead to exposure of sensitive user data, administrative functions, or other restricted areas. The blast radius depends on the sensitivity of the protected routes and the potential for lateral movement within the application. A successful exploit could be particularly damaging if the application handles personally identifiable information (PII) or financial data.

1. Gereserveerd2026-05-06
2. Gepubliceerd2026-05-13

The recommended mitigation for CVE-2026-44574 is to immediately upgrade Next.js to version 15.5.16 or 16.2.5. If upgrading is not immediately feasible, consider implementing stricter input validation and sanitization within your middleware functions to prevent query parameter manipulation. Review all dynamic routes protected by middleware and ensure that the logic correctly validates the route value. While not a direct fix, implementing a Web Application Firewall (WAF) with rules to detect and block suspicious query parameter patterns can provide an additional layer of defense. After upgrading, confirm the fix by attempting to access protected routes with crafted query parameters to verify that the middleware checks are functioning as expected.