CVE-2026-45109 Next.js: Middleware / Proxy bypass in App Router applications via segment-prefetch routes
Attackers can bypass middleware security checks in Next.js App Router applications using Turbopack via segment-prefetch routes.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-45109?
CVE-2026-45109 is a high-severity authentication bypass 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 15.2.0 to before 15.5.18 and 16.2.6, it was found that the fix addressing CVE-2026-44575 did not apply to middleware.ts with Turbopack. This vulnerability is fixed in 15.5.18 and 16.2.6.
Which versions are affected by CVE-2026-45109?
4 open source packages ship an affected version, including next. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
next npm | From 15.2.0 | 15.5.18 |
next npm | From 15.2.0 | 15.5.18 |
next npm | From 16.0.0 | 16.2.6 |
next npm | From 16.0.0 | 16.2.6 |
Products include Vercel Next.js.
How do I fix CVE-2026-45109?
Upgrade next to a fixed version for your release line: 15.5.18 or 16.2.6.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-45109 being exploited?
There is no known exploitation of CVE-2026-45109 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-ON69641, CLEANSTART-2026-RV40501, GHSA-26hh-7cqf-hhc6, MINI-57c6-5wg4-2xm8, MINI-74mq-6mvj-866x, MINI-778f-vjfj-mhpg and 2 more.