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AdonisJS BodyParser vulnerability
Complete RCE Exploit Analysis & Defense Explained Simply
🚨 Executive Summary: Critical RCE Vulnerability
A critical security flaw designated as CVE-2025-2009 (CVSS Score: 9.8) has been discovered in the BodyParser middleware of the AdonisJS Node.js framework. This vulnerability allows attackers to perform prototype pollution through specially crafted HTTP requests, which can be chained to achieve Remote Code Execution (RCE) on vulnerable servers. This comprehensive guide breaks down the technical exploit mechanics and provides actionable defense strategies.
📑 Table of Contents
- Understanding CVE-2025-2009: The Technical Breakdown
- How the Attack Works: Prototype Pollution to RCE Chain
- Technical Exploit Walkthrough with Code Analysis
- Real-World Attack Scenario & Impact
- Step-by-Step Patching & Mitigation Guide
- Red Team vs. Blue Team Perspective
- Common Mistakes & Security Best Practices
- Frequently Asked Questions (FAQ)
- Key Takeaways & Call to Action
1. Understanding CVE-2025-2009: The Technical Breakdown
The AdonisJS BodyParser vulnerability (CVE-2025-2009) is a prototype pollution flaw in the framework's request body parsing middleware. With a CVSS score of 9.8 (Critical), this vulnerability affects applications using AdonisJS versions before the security patch.
At its core, the BodyParser middleware is responsible for parsing incoming HTTP request data (JSON, form data, etc.) and making it available to application controllers. The flaw existed in how this parser handled nested objects during the merging process.
What is Prototype Pollution?
In JavaScript, every object inherits properties from a prototype. Prototype pollution occurs when an attacker can inject properties into this prototype chain, causing all objects to inherit these malicious properties. This can lead to:
- Property injection across the entire application
- Denial of Service through application crashes
- Remote Code Execution when combined with other vulnerabilities
- Authentication bypass and privilege escalation
2. How the Attack Works: Prototype Pollution to RCE Chain
The AdonisJS BodyParser vulnerability enables a multi-stage attack chain that transforms a seemingly benign JSON payload into full server compromise.
Stage 1: Initial Pollution Vector
The attacker sends a specially crafted HTTP POST request with a JSON payload containing prototype pollution primitives:
POST /api/user/profile HTTP/1.1
Content-Type: application/json
{
"user": "attacker",
"__proto__": {
"polluted": "malicious_value",
"toString": "malicious_function"
},
"constructor": {
"prototype": {
"admin": true
}
}
}
Stage 2: Parser Vulnerability Trigger
The vulnerable BodyParser recursively merges this data without sanitizing special JavaScript properties. The insecure merge function looks similar to this:
// VULNERABLE CODE (Simplified example)
function merge(target, source) {
for (const key in source) {
if (typeof source[key] === 'object' && source[key] !== null) {
// Recursive merge without prototype check
target[key] = merge(target[key] || {}, source[key]);
} else {
// Direct assignment - allows __proto__ injection
target[key] = source[key];
}
}
return target;
}
This function doesn't check if key equals __proto__ or constructor, allowing the pollution to occur.
Stage 3: From Pollution to Remote Code Execution
The polluted prototype becomes dangerous when combined with "gadgets" - code that uses polluted properties in dangerous ways. Common RCE pathways include:
- Template Engine Injection: If the app uses a template engine that evaluates properties from polluted objects
- Command Execution: When polluted properties flow into functions like
child_process.exec()oreval() - File System Operations: Polluted paths that lead to arbitrary file writes or reads
3. Technical Exploit Walkthrough with Code Analysis
The Complete Exploit Chain
Step 1: Reconnaissance & Target Identification
The attacker identifies an AdonisJS application through HTTP headers, error messages, or fingerprinting tools. Common indicators include:
X-Powered-By: AdonisJS
Server: AdonisJS
Error messages containing "Adonis" or "@adonisjs"
Step 2: Crafting the Poison Payload
The attacker creates a multi-layered payload that exploits the recursive merge vulnerability:
{
"normal_data": "value",
"__proto__": {
"execPath": "/bin/sh",
"NODE_OPTIONS": "--inspect=0.0.0.0:9229"
},
"constructor": {
"prototype": {
"shell": "bash",
"env": {"EVIL": "code"}
}
}
}
Step 3: Triggering RCE Through Existing Gadgets
After successful pollution, the attacker triggers code execution through various application features:
// Example vulnerable code pattern in the application
const userInput = req.body.templateName;
const template = require(`./templates/${Object.prototype[userInput]}`);
// If polluted: Object.prototype["../../etc/passwd"] = "../../etc/passwd"
4. Real-World Attack Scenario & Impact
Case Study: SaaS Platform Compromise
Consider a Software-as-a-Service platform built with AdonisJS that handles user data, payments, and administrative functions. An attacker discovers the platform through a routine web scan.
| Attack Phase | Technique Used | Impact |
|---|---|---|
| Initial Access | Send polluted JSON to user profile update endpoint | Pollutes the global Object prototype across the application |
| Privilege Escalation | Pollute authentication-related properties | Bypass authentication checks, gain admin access |
| Remote Code Execution | Chain pollution with template rendering function | Execute arbitrary commands on the server |
| Data Exfiltration | Use RCE to access databases and files | Steal sensitive user data, payment information |
| Persistence | Install backdoors, create new admin accounts | Maintain access even after initial vulnerability is patched |
5. Step-by-Step Patching & Mitigation Guide
Step 1: Immediate Vulnerability Assessment
Check your package.json for vulnerable AdonisJS packages:
"dependencies": {
"@adonisjs/core": "^5.9.0", // Check if < patched version
"@adonisjs/bodyparser": "^3.1.0" // Check if < patched version
}
Consult the official security advisory for exact vulnerable versions.
Step 2: Apply Security Updates
Update all affected packages to their patched versions:
npm update @adonisjs/core @adonisjs/bodyparser
# OR
yarn upgrade @adonisjs/core @adonisjs/bodyparser --latest
Verify the update by checking package-lock.json or yarn.lock for the new versions.
Step 3: Implement Input Validation
Add strict schema validation to all endpoints using AdonisJS Validator:
import { schema, validator } from '@adonisjs/validator'
const userSchema = schema.create({
username: schema.string(),
email: schema.string.email(),
// Explicitly reject unexpected properties
$$strict: true
})
// This will reject any request with __proto__ or constructor
Step 4: Deploy Web Application Firewall Rules
Configure WAF rules to block requests containing prototype pollution patterns:
- Block requests containing
"__proto__"in JSON keys - Block requests with
"constructor"and"prototype"patterns - Limit maximum request body size to prevent complex nested attacks
- Implement rate limiting on all endpoints
Step 5: Harden Server Configuration
- Run Node.js with the
--disable-proto=throwflag to prevent prototype pollution - Implement Content Security Policy (CSP) headers
- Use process isolation and containerization
- Apply the principle of least privilege for file system access
6. Red Team vs. Blue Team Perspective
🔴 Red Team (Attack) Perspective
- Discovery: Use automated scanners to find AdonisJS applications and test for the BodyParser vulnerability
- Payload Development: Create polymorphic payloads that evade basic WAF detection while maintaining exploit capability
- Lateral Movement: Once RCE is achieved, explore the network for additional targets and data
- Persistence: Install multiple backdoors and establish command & control channels
- Covering Tracks: Modify logs, use encrypted communication, and avoid detection systems
🔵 Blue Team (Defense) Perspective
- Threat Detection: Implement SIEM rules to detect prototype pollution patterns in web logs
- Patch Management: Establish automated security updates for all dependencies
- Runtime Protection: Use RASP (Runtime Application Self-Protection) solutions to block exploit attempts
- Incident Response: Develop playbooks specific to Node.js application compromises
- Forensic Readiness: Maintain comprehensive logging and monitoring for post-exploit analysis
7. Common Mistakes & Security Best Practices
❌ Common Security Mistakes
- Assuming middleware is secure: Trusting that built-in framework components don't need security review
- Insufficient input validation: Accepting user data without strict schema enforcement
- Delayed patching: Treating dependency updates as low-priority tasks
- Lack of monitoring: Not logging or alerting on suspicious request patterns
- Over-permissive CORS: Allowing requests from any origin without proper validation
✅ Security Best Practices
- Regular dependency audits: Use tools like Snyk or Dependabot for automated vulnerability scanning
- Defense in depth: Implement multiple security layers (WAF, input validation, output encoding)
- Security headers: Configure CSP, X-Frame-Options, X-Content-Type-Options headers
- Least privilege principle: Run applications with minimal necessary permissions
- Regular security training: Educate developers on secure coding practices and emerging threats
Pro Tip: Secure Merge Function Implementation
If you need to implement object merging in your code, use this secure pattern:
function safeMerge(target, source) {
for (const key in source) {
// Block prototype pollution attempts
if (key === '__proto__' || key === 'constructor' || key === 'prototype') {
continue;
}
if (typeof source[key] === 'object' && source[key] !== null) {
target[key] = safeMerge(target[key] || {}, source[key]);
} else {
target[key] = source[key];
}
}
return target;
}
8. Frequently Asked Questions (FAQ)
Q1: How can I test if my application is vulnerable without causing damage?
A: Use controlled security testing tools like Burp Suite with the "Prototype Pollution Scanner" extension, or run automated scanners in a development environment. Never test on production systems without explicit authorization.
Q2: Does this vulnerability affect other Node.js frameworks like Express or Fastify?
A: While this specific vulnerability is unique to AdonisJS, prototype pollution is a JavaScript anti-pattern that can affect any Node.js application with insecure object merging. Always validate and sanitize object operations in any framework.
Q3: What's the timeline for exploitation in the wild?
A: Critical vulnerabilities like CVE-2025-2009 typically see exploitation attempts within 24-72 hours of public disclosure. Automated scanning for this vulnerability began immediately after the advisory was published.
Q4: Can firewalls or network security appliances block this attack?
A: Traditional network firewalls cannot effectively block this attack because it uses legitimate HTTP requests. However, Web Application Firewalls (WAFs) with custom rules can detect and block prototype pollution patterns in request bodies.
Q5: What should I do if I suspect my server has been compromised?
A: Immediately follow your incident response plan: 1) Isolate the affected system, 2) Preserve forensic evidence, 3) Rotate all credentials and keys, 4) Conduct a thorough security audit, 5) Rebuild systems from clean backups, 6) Implement additional monitoring.
9. Key Takeaways & Call to Action
🎯 Critical Summary
- The AdonisJS BodyParser vulnerability (CVE-2025-2009) is a critical prototype pollution flaw with CVSS 9.8 score
- Successful exploitation can lead to Remote Code Execution (RCE) and complete server compromise
- The attack chain involves: 1) Polluting Object.prototype → 2) Finding exploit gadgets → 3) Achieving code execution
- All AdonisJS applications using vulnerable versions must be patched immediately
- Defense in depth with multiple security layers is essential for comprehensive protection
🚀 Immediate Action Plan
Priority 1: Assessment & Patching (Today)
- Inventory all AdonisJS applications in your environment
- Check and update all dependencies to patched versions
- Validate that the patch is correctly applied and functioning
Priority 2: Defense Implementation (This Week)
- Implement input validation schemas for all API endpoints
- Configure WAF rules to block prototype pollution patterns
- Review and harden server security configurations
Priority 3: Long-Term Security (Ongoing)
- Establish automated dependency vulnerability scanning
- Implement comprehensive logging and monitoring
- Conduct regular security training for development teams
- Perform periodic security assessments and penetration testing
Additional Resources for Security Professionals
- OWASP Top 10 2021 - Essential web application security risks
- PortSwigger: Prototype Pollution - Detailed technical guide
- AdonisJS Security Advisories - Official security updates
- CVE-2025-2009 Official Record - National vulnerability database entry
- Synopsys: Understanding Prototype Pollution - Comprehensive analysis
Stay vigilant, patch promptly, and implement defense in depth. The AdonisJS BodyParser vulnerability serves as a critical reminder that framework components require the same security scrutiny as custom code.
Share this guide with your development and security teams to ensure comprehensive protection against this and similar vulnerabilities.
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