CVE-2021-20086
📋 TL;DR
CVE-2021-20086 is a prototype pollution vulnerability in jquery-bbq 1.2.1 that allows attackers to inject malicious properties into Object.prototype. This can lead to various client-side attacks including cross-site scripting (XSS) and potentially remote code execution. Any web application using the vulnerable jquery-bbq library is affected.
💻 Affected Systems
- jquery-bbq
📦 What is this software?
Jquery Bbq by Jquery Bbq Project
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution in the browser context, complete compromise of user sessions, and potential server-side impact if combined with other vulnerabilities.
Likely Case
Cross-site scripting attacks leading to session hijacking, credential theft, and client-side data manipulation.
If Mitigated
Limited impact with proper content security policies, input validation, and modern browser security features.
🎯 Exploit Status
Public proof-of-concept exists in the BlackFan repository. Exploitation requires user interaction (visiting a malicious page) but no authentication.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: No official patch - library is deprecated
Vendor Advisory: https://github.com/cowboy/jquery-bbq
Restart Required: No
Instructions:
1. Remove jquery-bbq 1.2.1 from your application. 2. Replace with alternative libraries or implement functionality natively. 3. Update all HTML/JavaScript files to remove references to jquery-bbq.
🔧 Temporary Workarounds
Input Sanitization
allImplement strict input validation and sanitization for all user-controlled data before processing with jquery-bbq functions.
Content Security Policy
allImplement strict Content Security Policy headers to mitigate XSS impact.
Content-Security-Policy: default-src 'self'; script-src 'self'
🧯 If You Can't Patch
- Implement WAF rules to detect and block prototype pollution payloads
- Use browser extensions or security headers to prevent execution of malicious scripts
🔍 How to Verify
Check if Vulnerable:
Check your web application's source code for references to jquery-bbq version 1.2.1. Search for script tags or import statements containing 'jquery-bbq' or 'bbq'.Check Version:
grep -r 'jquery-bbq\|bbq' /path/to/webroot/ | grep -i versionVerify Fix Applied:
Verify that jquery-bbq 1.2.1 is no longer loaded by your application. Check browser developer tools Network tab to confirm no requests for the vulnerable library.📡 Detection & Monitoring
Log Indicators:
- Unusual JavaScript errors related to Object.prototype
- Multiple failed attempts to access prototype methods
Network Indicators:
- Requests containing __proto__ or constructor payloads in URLs or POST data
- Unusual JavaScript file loads
SIEM Query:
web_logs | where url contains "__proto__" or url contains "constructor" or post_data contains "__proto__"