How the Mentioned CVE Works:
The CVE-2025-XXXX vulnerability in Next.js allows attackers to bypass authorization checks implemented in middleware. This occurs due to improper handling of the `x-middleware-subrequest` header. When this header is present in an external user request, the middleware fails to enforce authorization checks, granting unauthorized access to protected routes or resources. The vulnerability affects Next.js versions >= 11.1.4, <= 13.5.6, >= 14.0, < 14.2.25, and >= 15.0, < 15.2.3. Patched versions (14.2.25 and 15.2.3) address this issue by validating the header and ensuring proper authorization enforcement.
DailyCVE Form:
Platform: Next.js
Version: 11.1.4 – 13.5.6, 14.0 – 14.2.24, 15.0 – 15.2.2
Vulnerability: Authorization Bypass
Severity: Critical
Date: Mar 21, 2025
What Undercode Say:
Exploitation:
1. Exploit Code Example:
curl -H "x-middleware-subrequest: true" http://target-nextjs-app.com/protected-route
This command sends a request with the malicious header to bypass middleware checks.
2. Exploit Impact:
- Unauthorized access to sensitive routes.
- Potential data leaks or privilege escalation.
3. Exploit Mitigation:
- Block requests containing the `x-middleware-subrequest` header at the reverse proxy level.
- Example for Nginx:
location / { if ($http_x_middleware_subrequest) { return 403; } }
Protection:
1. Update Next.js:
Upgrade to patched versions (14.2.25 or 15.2.3).
2. Middleware Workaround:
Add custom validation in middleware to reject requests with the `x-middleware-subrequest` header:
export function middleware(req) {
if (req.headers.get('x-middleware-subrequest')) {
return new Response('Unauthorized', { status: 403 });
}
}
3. Reverse Proxy Configuration:
Use a reverse proxy like Nginx or Apache to filter malicious headers before they reach the Next.js app.
4. Monitoring:
Implement logging for requests with the `x-middleware-subrequest` header to detect potential exploitation attempts.
5. Code Review:
Regularly review middleware logic to ensure proper authorization checks are in place.
6. Security Headers:
Add security headers to mitigate other potential attacks:
res.setHeader('X-Content-Type-Options', 'nosniff');
res.setHeader('X-Frame-Options', 'DENY');
7. Automated Testing:
Use tools like OWASP ZAP or Burp Suite to test for authorization bypass vulnerabilities.
8. Patch Management:
Subscribe to Next.js security advisories to stay informed about future vulnerabilities.
9. Incident Response:
Develop a response plan for unauthorized access incidents, including rollback procedures.
10. Community Awareness:
Share this CVE with your development team to ensure everyone is aware of the risks and mitigation steps.
By following these steps, you can protect your Next.js application from this critical vulnerability and ensure robust security practices.
References:
Reported By: https://github.com/advisories/GHSA-f82v-jwr5-mffw
Extra Source Hub:
Undercode
