CVE-2026-64643 Next.js: Unauthenticated Disclosure of Internal Server Function endpoints
Unauthenticated attackers can disclose internal Server Action endpoints in Next.js App Router applications, bypassing page-level authentication controls.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-64643?
CVE-2026-64643 is a medium-severity vulnerability in Vercel Next.js, published on 27 Jul 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. In versions 12.0.0 through 15.5.20 and 16.0.0 through 16.2.10, Next.js applications using App Router, Server Actions (use server) or use cache endpoints can be disclosed bypassing any authentication on the pages where these endpoints are usually used. Server Action IDs can be disclosed to unauthenticated users via publicly served client artifacts (for example, static chunks containing action references). Affected users are applications using App Router and Server Actions. By itself, this disclosure is typically a recon/enumeration primitive; however, it can increase risk when combined with other weaknesses. This issue has been fixed in versions 15.5.21 and 16.2.11.
Weakness: CWE-201
Which versions are affected by CVE-2026-64643?
4 open source packages ship an affected version, including next. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
next npm | From 13.0.0 | 15.5.21 |
next npm | From 13.0.0 | 15.5.21 |
next npm | From 16.0.0 | 16.2.11 |
next npm | From 16.0.0 | 16.2.11 |
Products include Vercel Next.js.
How do I fix CVE-2026-64643?
Upgrade next to a fixed version for your release line: 15.5.21 or 16.2.11.
Is CVE-2026-64643 being exploited?
There is no known exploitation of CVE-2026-64643 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-BM18336, CLEANSTART-2026-LF50543, ECHO-9c66-41a7-0eec, GHSA-955p-x3mx-jcvp, MINI-2fx4-j5jv-6p5h, MINI-4cg3-rc6f-xg6p and 3 more.