CVE-2026-44573 Next.js: Middleware / Proxy bypass in Pages Router applications using i18n
Attackers can bypass middleware authorization checks to access protected SSR JSON data in Next.js Pages Router applications using i18n.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-44573?
CVE-2026-44573 is a high-severity missing authorization vulnerability in Vercel Next.js, published on 13 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Which versions are affected by CVE-2026-44573?
4 open source packages ship an affected version, including next. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
next npm | From 12.2.0 | 15.5.16 |
next npm | From 12.2.0 | 15.5.16 |
next npm | From 16.0.0 | 16.2.5 |
next npm | From 16.0.0 | 16.2.5 |
Products include Vercel Next.js.
How do I fix CVE-2026-44573?
Upgrade next to a fixed version for your release line: 15.5.16 or 16.2.5.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2026-44573 being exploited?
There is no known exploitation of CVE-2026-44573 in the wild and no public exploit code.
Other vulnerabilities in Vercel Next.js
- CVE-2025-29927 Authorization Bypass in Next.js Middleware
- CVE-2026-44578 Next.js: Server-side request forgery in applications using WebSocket upgrades
- CVE-2026-94483 Next.js: Server-Side Request Forgery in Image Optimization
- CVE-2026-64642 Next.js: Middleware / Proxy bypass in App Router applications using Turbopack and single locale
- CVE-2026-64645 Next.js: Server-Side Request Forgery in rewrites via attacker-controlled destination hostname
Sources
Also known as CLEANSTART-2026-CN04690, CLEANSTART-2026-OT89154, GHSA-36qx-fr4f-26g5, MINI-2746-qvcp-ghwp, MINI-fh3g-pvp7-hjrj, MINI-x4vh-44jg-56cf and 2 more.