CVE-2026-44573
Next.js: Middleware / Proxy bypass in Pages Router applications using i18n
CVSS Score
7.5
EPSS Score
0.0%
EPSS Percentile
0th
Next.js is a React framework for building full-stack web applications. From 12.2.0 to before 15.5.16 and 16.2.5, 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. This vulnerability is fixed in 15.5.16 and 16.2.5.
| CWE | CWE-863 |
| Vendor | vercel |
| Product | next.js |
| Published | May 13, 2026 |
| Last Updated | May 13, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None
Affected Versions
vercel / next.js
>= 12.2.0, < 15.5.16 >= 16.0.0, < 16.2.5