CVE-2026-44573

Workarounds

If you cannot upgrade immediately, enforce authorization in the page's server-side data path instead of relying solely on middleware.

Applications using the Pages Router with i18n configured and middleware/proxy-based authorization can allow unauthorized access to protected page data through locale-less /_next/data/<buildId>/<page>.json requests. In affected configurations, middleware does not run for the unprefixed data route, allowing an attacker to retrieve SSR JSON for protected pages without passing the intended authorization checks.

The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions. Typical impact: unauthorized data access or execution of privileged operations.

CVE-2026-44573 has a CVSS score of 7.5 (High). 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 matcher logic was updated to perform the same match as it would on a non-i18n data route.

1. What is CVE-2026-44573? CVE-2026-44573 is a high-severity incorrect authorization vulnerability in next (npm), affecting versions >= 12.2.0, < 15.5.16. It is fixed in 15.5.16, 16.2.5. The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions.
2. How severe is CVE-2026-44573? CVE-2026-44573 has a CVSS score of 7.5 (High). 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-2026-44573? next (npm) versions >= 12.2.0, < 15.5.16 is affected.
4. Is there a fix for CVE-2026-44573? Yes. CVE-2026-44573 is fixed in 15.5.16, 16.2.5. Upgrade to this version or later.
5. Is CVE-2026-44573 exploitable, and should I be worried? Whether CVE-2026-44573 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-2026-44573 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-2026-44573?
   • Upgrade next to 15.5.16 or later
   • Upgrade next to 16.2.5 or later