CVE-2020-28461
📋 TL;DR
CVE-2020-28461 is a prototype pollution vulnerability in the js-ini package that allows attackers to inject malicious properties into JavaScript objects by submitting specially crafted INI files. This affects any application using js-ini versions before 1.3.0 to parse INI files, potentially leading to denial of service, remote code execution, or privilege escalation depending on how the polluted objects are used.
💻 Affected Systems
- js-ini package
📦 What is this software?
Js Ini by Js Ini Project
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise if polluted objects are used in security-critical contexts like authentication or command execution.
Likely Case
Denial of service through application crashes or unpredictable behavior, with potential for data manipulation in affected applications.
If Mitigated
Limited impact with proper input validation and sandboxing, potentially only causing application instability.
🎯 Exploit Status
Exploitation requires the ability to submit INI files to an application using js-ini. The vulnerability is well-documented with public proof-of-concept examples available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 1.3.0 and later
Vendor Advisory: https://github.com/Sdju/js-ini/commit/fa17efb7e3a7c9464508a254838d4c231784931e
Restart Required: Yes
Instructions:
1. Update js-ini package to version 1.3.0 or later using npm update js-ini. 2. Restart all Node.js applications using js-ini. 3. Test INI parsing functionality to ensure compatibility.
🔧 Temporary Workarounds
Input validation and sanitization
allImplement strict validation of INI file content before parsing, rejecting files with suspicious patterns.
Use Object.freeze() on prototypes
allFreeze Object.prototype and other relevant prototypes to prevent pollution.
Object.freeze(Object.prototype);
🧯 If You Can't Patch
- Implement strict input validation to reject INI files containing __proto__ or constructor properties.
- Use alternative INI parsing libraries that are not vulnerable to prototype pollution.
🔍 How to Verify
Check if Vulnerable:
Check package.json for js-ini version <1.3.0 or run npm list js-ini to see installed version.Check Version:
npm list js-ini | grep js-iniVerify Fix Applied:
Verify js-ini version is 1.3.0 or higher using npm list js-ini and test parsing known malicious INI files.📡 Detection & Monitoring
Log Indicators:
- Unexpected application crashes during INI parsing
- Unusual property assignments in object logs
- Errors related to prototype modifications
Network Indicators:
- Unusual INI file uploads to applications
- POST requests with INI content to parsing endpoints
SIEM Query:
source="application.logs" AND ("js-ini" OR "INI parsing") AND ("crash" OR "error" OR "unexpected")