CVE-2021-20087
📋 TL;DR
CVE-2021-20087 is a prototype pollution vulnerability in jquery-deparam 0.5.1 that allows attackers to inject properties into Object.prototype. This can lead to various security issues including denial of service, remote code execution, or privilege escalation. Applications using this vulnerable library for parsing URL parameters are affected.
💻 Affected Systems
- jquery-deparam
📦 What is this software?
Jquery Deparam by Acemetrix
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise, data theft, or ransomware deployment.
Likely Case
Denial of service, application instability, or privilege escalation within the application context.
If Mitigated
Limited impact with proper input validation and security controls, potentially causing only application errors.
🎯 Exploit Status
Exploitation requires sending specially crafted URL parameters to applications using the vulnerable library.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 0.5.2 and later
Vendor Advisory: https://github.com/BlackFan/client-side-prototype-pollution/blob/master/pp/jquery-deparam.md
Restart Required: No
Instructions:
1. Update jquery-deparam to version 0.5.2 or later. 2. Update package.json to specify ^0.5.2. 3. Run npm update jquery-deparam. 4. Test application functionality.
🔧 Temporary Workarounds
Input validation and sanitization
allImplement strict input validation for URL parameters before passing to jquery-deparam
Use alternative library
allReplace jquery-deparam with a secure alternative like qs or URLSearchParams
npm uninstall jquery-deparam
npm install qs
🧯 If You Can't Patch
- Implement WAF rules to block requests with suspicious parameter patterns
- Isolate affected applications behind reverse proxies with strict input filtering
🔍 How to Verify
Check if Vulnerable:
Check package.json or package-lock.json for jquery-deparam version 0.5.1Check Version:
npm list jquery-deparamVerify Fix Applied:
Verify jquery-deparam version is 0.5.2 or later in package.json and node_modules📡 Detection & Monitoring
Log Indicators:
- Unusual parameter patterns in URL logs
- Application errors related to object property access
Network Indicators:
- Requests with specially crafted __proto__ or constructor parameters
SIEM Query:
url:*__proto__* OR url:*constructor* OR parameters:*__proto__*🔗 References
- https://github.com/BlackFan/client-side-prototype-pollution/blob/master/pp/jquery-deparam.md
- https://github.com/BlackFan/client-side-prototype-pollution/blob/master/pp/jquery-deparam.md
- https://github.com/RetireJS/retire.js/blob/6da45fcb6a3425e55ee8181b2ac35168879bf086/repository/jsrepository-master.json#L824-L842
