CVE-2023-26135
📋 TL;DR
CVE-2023-26135 is a prototype pollution vulnerability in the flatnest npm package that allows attackers to modify object prototypes, potentially leading to denial of service, remote code execution, or privilege escalation. All versions of flatnest are affected, impacting any Node.js application using this package for object flattening/nesting operations. The vulnerability exists in the nest() function which doesn't properly validate user input.
💻 Affected Systems
- flatnest npm package
📦 What is this software?
Flatnest by Flatnest Project
⚠️ Manual Verification Required
This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.
Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).
🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.
- Review the CVE details at NVD
- Check vendor security advisories for your specific version
- Test if the vulnerability is exploitable in your environment
- Consider updating to the latest version as a precaution
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise, data exfiltration, and lateral movement within the network.
Likely Case
Denial of service through application crashes or unexpected behavior, potentially allowing privilege escalation within the application context.
If Mitigated
Limited impact with proper input validation and sandboxing, potentially causing only application instability.
🎯 Exploit Status
Proof of concept available in GitHub issues. Exploitation requires the application to process attacker-controlled input through the vulnerable function.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Version with commit 27d569baf9d9d25677640edeaf2d13af165868d6
Vendor Advisory: https://github.com/brycebaril/node-flatnest/commit/27d569baf9d9d25677640edeaf2d13af165868d6
Restart Required: Yes
Instructions:
1. Update flatnest package to patched version: npm update flatnest
2. Restart your Node.js application
3. Verify the fix by checking package.json for updated version
🔧 Temporary Workarounds
Input validation wrapper
allWrap flatnest.nest() calls with input validation to reject objects with __proto__ or constructor properties
// JavaScript code to wrap vulnerable function
function safeNest(input) {
if (typeof input !== 'object' || input === null) return input;
// Validate input doesn't contain prototype pollution keys
const jsonStr = JSON.stringify(input);
if (jsonStr.includes('__proto__') || jsonStr.includes('constructor')) {
throw new Error('Invalid input: potential prototype pollution');
}
return flatnest.nest(input);
}
🧯 If You Can't Patch
- Implement strict input validation for all data passed to flatnest.nest() function
- Use object-freeze or similar techniques to prevent prototype modification in critical objects
🔍 How to Verify
Check if Vulnerable:
Check package.json or run: npm list flatnest | grep flatnestCheck Version:
npm list flatnestVerify Fix Applied:
Verify the installed version contains commit 27d569b or run: npm list flatnest | grep -E 'flatnest@[0-9]+\.[0-9]+\.[0-9]+' and compare with latest version📡 Detection & Monitoring
Log Indicators:
- Unusual application crashes, unexpected object property modifications, error logs containing 'flatnest' or 'nest' function failures
Network Indicators:
- Unusual HTTP requests containing nested objects with __proto__ or constructor properties
SIEM Query:
source="application_logs" AND ("flatnest" OR "prototype" OR "__proto__") AND (error OR crash OR exception)🔗 References
- https://github.com/brycebaril/node-flatnest/blob/b7d97ec64a04632378db87fcf3577bd51ac3ee39/nest.js%23L43
- https://github.com/brycebaril/node-flatnest/commit/27d569baf9d9d25677640edeaf2d13af165868d6
- https://github.com/brycebaril/node-flatnest/issues/4
- https://security.snyk.io/vuln/SNYK-JS-FLATNEST-3185149
- https://github.com/brycebaril/node-flatnest/blob/b7d97ec64a04632378db87fcf3577bd51ac3ee39/nest.js%23L43
- https://github.com/brycebaril/node-flatnest/commit/27d569baf9d9d25677640edeaf2d13af165868d6
- https://github.com/brycebaril/node-flatnest/issues/4
- https://security.snyk.io/vuln/SNYK-JS-FLATNEST-3185149
