CVE-2025-30218

Next.js may leak x-middleware-subrequest-id to external hosts

Verified by Precogs Threat Research
Last Updated: Oct 13, 2025
Base Score
8.1HIGH

Executive Summary

CVE-2025-30218 is a high severity vulnerability affecting appsec. It is classified as an undisclosed flaw. Ensure your systems and dependencies are patched immediately to mitigate exposure risks.

Precogs AI Insight

"Precogs AI Analysis Engine identifies web application vulnerabilities through semantic code analysis, detecting injection flaws, broken authentication, and insecure data flows across your entire codebase."

Exploit Probability
Elevated (52%)
Public POC
Undisclosed
Exploit Probability
Elevated (52%)
Public POC
Available
Affected Assets
appsecNVD Database

What is this vulnerability?

CVE-2025-30218 is categorized as a critical Application Verification Flaw flaw. Based on our vulnerability intelligence, this issue occurs when the application fails to securely handle untrusted data boundaries.

Summary In the process of remediating CVE-2025-29927, we looked at other possible exploits of Middl.

This architectural defect enables adversaries to bypass intended security controls, directly manipulating the application's execution state or data layer. Immediate strategic intervention is required.

Risk Assessment

MetricValue
CVSS Base Score8.1 (HIGH)
Vector StringN/A
PublishedApril 2, 2025
Last ModifiedOctober 13, 2025
Related CWEsN/A

Impact on Systems

Unauthorized Access: Flaws in application logic can permit unauthorized interaction with protected APIs.

Data Manipulation: Adversaries may alter critical application states, such as user roles or configurations.

Service Disruption: Improper error handling or unvalidated inputs can lead to resource exhaustion.

How to fix this issue?

Implement the following strategic mitigations immediately to eliminate the attack surface.

1. Defense in Depth Implement multi-layered validation (client-side, API gateway, and server-side).

2. Least Privilege Ensure backend service accounts operate with the absolute minimum rights required.

3. Security Regression Testing Integrate automated semantic security scanning into the deployment pipeline.

Vulnerability Signature

// Generic Application Security Flaw (Node.js)
app.post('/api/update-profile', (req, res) =\> \{
    // DANGEROUS: Mass Assignment / Object Injection
    // Attacker can pass \{ "isAdmin": true, "email": "..." \}
    User.update(\{ id: req.user.id \}, req.body);
    
    // SECURED: Explicitly select permitted fields
    const \{ email, displayName, bio \} = req.body;
    User.update(\{ id: req.user.id \}, \{ email, displayName, bio \});
\});

References and Sources