CVE-2021-25927
📋 TL;DR
CVE-2021-25927 is a prototype pollution vulnerability in the 'safe-flat' npm package versions 2.0.0 through 2.0.1. This allows attackers to modify object prototypes, potentially leading to denial of service or remote code execution. Anyone using vulnerable versions of this package in their Node.js applications is affected.
💻 Affected Systems
- safe-flat npm package
📦 What is this software?
Safe Flat by Safe Flat Project
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise, data theft, or ransomware deployment.
Likely Case
Denial of service through application crashes or instability, with potential for limited code execution in specific configurations.
If Mitigated
Limited impact if input validation and sandboxing prevent malicious payloads from reaching vulnerable functions.
🎯 Exploit Status
Prototype pollution vulnerabilities are well-understood and often have public proof-of-concept exploits available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2.0.2 and later
Vendor Advisory: https://github.com/jessie-codes/safe-flat/commit/4b9b7db976bba8c968354f4315f5f9c219b7cbf3
Restart Required: Yes
Instructions:
1. Update package.json to require safe-flat version 2.0.2 or later. 2. Run 'npm update safe-flat' or 'yarn upgrade safe-flat'. 3. Restart your Node.js application.
🔧 Temporary Workarounds
Input validation and sanitization
allImplement strict input validation to prevent malicious objects from reaching the safe-flat functions.
🧯 If You Can't Patch
- Implement network segmentation to isolate vulnerable systems
- Deploy web application firewall with prototype pollution detection rules
🔍 How to Verify
Check if Vulnerable:
Check package.json or package-lock.json for safe-flat version 2.0.0 or 2.0.1Check Version:
npm list safe-flatVerify Fix Applied:
Verify safe-flat version is 2.0.2 or later in package.json and node_modules📡 Detection & Monitoring
Log Indicators:
- Unusual application crashes
- Unexpected prototype modifications in JavaScript error logs
Network Indicators:
- Unusual HTTP requests containing nested objects with __proto__ or constructor properties
SIEM Query:
source="application.logs" AND ("prototype pollution" OR "safe-flat" OR "CVE-2021-25927")🔗 References
- https://github.com/jessie-codes/safe-flat/commit/4b9b7db976bba8c968354f4315f5f9c219b7cbf3
- https://www.whitesourcesoftware.com/vulnerability-database/CVE-2021-25927
- https://github.com/jessie-codes/safe-flat/commit/4b9b7db976bba8c968354f4315f5f9c219b7cbf3
- https://www.whitesourcesoftware.com/vulnerability-database/CVE-2021-25927
