Next.js: Middleware / Proxy bypass in Pages Router applications using i18n
Title source: cnaExploitation Summary
EIP tracks 2 public exploits for CVE-2026-44573. PoCs published by dwisiswant0, XZ1r0.
AI-analyzed exploit summary This repository contains functional proof-of-concept exploits for multiple Next.js vulnerabilities, including CVE-2026-44573, which involves a Pages Router i18n data-route bypass. The PoCs include detailed write-ups, vulnerable code excerpts, and runnable exploit scripts.
Description
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.
Exploits (2)
This repository contains functional proof-of-concept exploits for multiple Next.js vulnerabilities, including CVE-2026-44573, which involves a Pages Router i18n data-route bypass. The PoCs include detailed write-ups, vulnerable code excerpts, and runnable exploit scripts.
This repository contains a functional exploit for CVE-2026-44573, which bypasses middleware authentication in Next.js Pages Router applications with i18n configuration by exploiting a gap in the middleware matcher regex for locale-prefixed data URLs.
References (1)
Scores
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N