CVE-2026-25521
📋 TL;DR
Locutus versions 2.0.12 through 2.0.38 contain a prototype pollution vulnerability that allows attackers to modify JavaScript object prototypes via crafted input. This affects applications using Locutus for educational JavaScript functionality. Attackers could potentially inject malicious properties into objects used throughout the application.
💻 Affected Systems
- locutus
📦 What is this software?
Locutus by Locutus
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution, denial of service, or privilege escalation by polluting global object prototypes and altering application behavior.
Likely Case
Application instability, unexpected behavior, or denial of service through prototype pollution affecting object inheritance chains.
If Mitigated
Limited impact if input validation and sanitization are implemented, though prototype pollution could still cause unexpected behavior.
🎯 Exploit Status
Exploitation requires crafting specific input to bypass previous prototype pollution mitigations using String.prototype.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2.0.39
Vendor Advisory: https://github.com/locutusjs/locutus/security/advisories/GHSA-rxrv-835q-v5mh
Restart Required: No
Instructions:
1. Update locutus dependency to version 2.0.39 or later. 2. Run npm update locutus or yarn upgrade locutus. 3. Test application functionality after update.
🔧 Temporary Workarounds
Input validation and sanitization
allImplement strict input validation to reject any input containing prototype pollution patterns or suspicious property names.
🧯 If You Can't Patch
- Implement strict input validation and sanitization for all user-provided data processed by locutus functions.
- Monitor application logs for unexpected behavior or errors related to object property access.
🔍 How to Verify
Check if Vulnerable:
Check package.json or node_modules/locutus/package.json for version number between 2.0.12 and 2.0.38 inclusive.Check Version:
npm list locutus | grep locutus or check package.json directlyVerify Fix Applied:
Verify locutus version is 2.0.39 or higher in package.json and test application with known malicious inputs.📡 Detection & Monitoring
Log Indicators:
- Unexpected property access errors
- Type errors related to object prototypes
- Application crashes or instability
Network Indicators:
- Unusual input patterns in HTTP requests containing prototype pollution payloads
SIEM Query:
Search for error logs containing 'prototype', 'TypeError', or 'Cannot set property' in application logs.