The Next.js and React ecosystem is currently dealing with a severe Remote Code Execution (RCE) vulnerability that we are calling React2Shell (tracked as CVE-2025-66478).
If your production application uses the App Router, immediate action is required.
What is React2Shell?
This is a high-severity (CVSS 10.0) insecure deserialization flaw.
When your Next.js server processes data for React Server Components (RSC), an attacker can exploit this process by injecting specially crafted data. The server misinterprets this data as valid code and executes it, granting the attacker RCE privileges.
Impact: Complete server compromise, including data theft and system takeover.
The Immediate Patch Plan (3 Steps)
- Update Core Packages You must update your Next.js and React packages to the latest patched versions.
Recommended Method (Utility):
Bash
npx fix-react2shell-next
Manual Update (For Strict Control):
Bash
npm install next@latest react@latest react-dom@latest
Verify you are on next@16.0.7 or later
- Understand Edge Protection (Vercel Users) If you are hosted on Vercel, platform-level Web Application Firewall (WAF) rules have been deployed to act as a temporary shield against known exploit patterns.
⚠️ Important: The WAF is a temporary fix. The vulnerability remains in your application code until you apply the code updates in Step 1. Do not skip the dependency update.
- Post-Patch Hygiene If your app was running a vulnerable version, assume a breach may have occurred:
Rotate Secrets: Immediately change all sensitive keys (DB_URL, API_KEYs, etc.) in your environment variables.
Audit Logs: Review server logs for unusual POST requests or unexpected shell commands.
Stay Secure
Security requires continuous effort. Leveraging modern tools like TypeScript across the stack helps prevent entire classes of security vulnerabilities before they are even deployed.
This alert is brought to you by the team at WebMixStudio, specializing in secure Next.js development. Stay safe and patch your apps!
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