A major security update has just landed for the entire Next.js community. A critical React Server Components (RSC) vulnerability — CVE-2025-66478, rated CVSS 10.0 (highest severity) — has been identified. This flaw opens the door to potential remote code execution (RCE) in unpatched environments, making it one of the most urgent issues developers must address.
The good news? Next.js has released freshly patched versions across all major release lines, ensuring teams can update immediately. If your project uses the App Router with RSC, updating isn’t optional — it’s essential.
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⚠️ What Exactly Happened?
The vulnerability originates from React itself (CVE-2025-55182) and affects the RSC protocol implemented inside Next.js.
When untrusted inputs were processed on the server, attackers could manipulate execution paths and potentially run malicious code.
This makes it one of the most serious security issues in Next.js history.
📌 Affected Versions :
You are vulnerable if your project uses React Server Components + App Router with:
- Next.js 15.x
- Next.js 16.x
- Next.js 14.3.0-canary.77 and later canaries
❌ Not affected:
- Next.js 13.x
- Next.js 14.x stable
- Pages Router projects
- Edge Runtime apps
🟢 New Patched Versions Released Today
Next.js has released fully hardened, secure versions that fix the RSC protocol.
✅ Patch Versions Available Now
15.0.5 15.1.9 15.2.6 15.3.6 15.4.8 15.5.7 16.0.7
These updates contain:
- ✔️ Hardened RSC protocol
- ✔️ Safer server-side input validation
- ✔️ Updated stable React patches
- ✔️ Improved App Router pipeline
- ✔️ Reduced attack surface for RCE
📉 If you're on a Canary Version
Downgrade immediately:
npm install next@14
Canary builds contain the vulnerable RSC runtime.
🧭 What’s New in the Latest Version?
The new Next.js security release includes:
🔐 Stronger Security Layers
- Better RSC request parsing
- Isolated server execution
- Improved SSR streaming checks
⚙️ Performance + Stability Fixes
- More stable RSC hydration
- Fewer server misalignment issues
- Cleaner App Router behavior
🛠️ Developer-Focused Improvements
- More predictable server logs
- Better debugging visibility
- Smoother build pipeline updates
These updates strengthen the security foundation for the server-first architecture that Next.js has been building toward.
🔧 Required Action :
✔️ 1. Update to the latest patched version
Choose the patched version for your release line.
✔️ 2. Rebuild & redeploy your app
Ensure patched code runs on your server.
✔️ 3. Avoid canary releases
They contain the vulnerable protocol.
✔️ 4. Monitor Next.js security advisories
Security updates can come anytime.
🔍 Why This Matters for Developers
Next.js is moving deeper into server-driven UI, and React Server Components are the backbone of that architecture.
When an RSC protocol issue happens, server execution becomes exposed — which is why this vulnerability is taken so seriously.
This update is not just a patch — it’s a step forward for the framework’s long-term stability and security.
💡Conclusion: Update Today. Stay Secure.
This is a high-severity, high-priority update.
If you are using the App Router with RSC, updating is not optional.
✔️ Update your Next.js version
✔️ Rebuild and redeploy
✔️ Avoid canaries
✔️ Follow security updates
Your users and your application security depend on it.
Tags
Next.js security updateNext.js vulnerability 2025CVE-2025-66478 fixNext.js RSC vulnerabilityReact Server Components securityNext.js latest version 2025Next.js patch releaseupdate Next.js safely.
Vijay Balpande
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