Overview
About vulnerability
Impact
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.
Fix
The matcher logic was updated to perform the same match as it would on a non-i18n data route.
Workarounds
If you cannot upgrade immediately, enforce authorization in the page’s server-side data path instead of relying solely on middleware.
Details
- Affected product:
- Next.js
- Affected packages:
- create-next-app @ 12.3.7 (+125 more)