CVE-2026-31865

What is this vulnerability?

CVE-2026-31865 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.

Elysia is a Typescript framework for request validation, type inference, OpenAPI documentation, and client-server communication. Prior to version 1.4.27, a...

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

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

• NVD — CVE-2026-31865
• MITRE — CVE-2026-31865
• CWE-1321 — MITRE CWE
• CWE-1321 Details
• Application Security Vulnerabilities
• AI Code Security Vulnerabilities

Vulnerability Code Signature

Attack Data Flow

Vulnerable Code Pattern

// ❌ VULNERABLE: Prototype Pollution
function merge(target, source) {
  for (let key in source) {
    // Taint sink: recursively merges without sanitizing __proto__
    if (typeof source[key] === 'object') {
      if (!target[key]) target[key] = {};
      merge(target[key], source[key]);
    } else {
      target[key] = source[key];
    }
  }
}

Secure Code Pattern

// ✅ SECURE: Safe Merge
function merge(target, source) {
  for (let key in source) {
    // Sanitized validation: block dangerous properties
    if (key === '__proto__' || key === 'constructor' || key === 'prototype') continue;
    if (typeof source[key] === 'object') {
      if (!target[key]) target[key] = {};
      merge(target[key], source[key]);
    } else {
      target[key] = source[key];
    }
  }
}

How Precogs Detects This

Precogs AI Analysis Engine detects unsafe object merging patterns native to JavaScript, preventing Prototype Pollution.\n