CVE-2021-29326
📋 TL;DR
CVE-2021-29326 is a heap buffer overflow vulnerability in Moddable's fxIDToString function that allows attackers to execute arbitrary code or cause denial of service. This affects applications built with Moddable SDK v10.5.0 that process untrusted input. Developers using this JavaScript engine for IoT or embedded systems are primarily impacted.
💻 Affected Systems
- Moddable SDK
📦 What is this software?
Moddable by Moddable
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise, data theft, or device takeover
Likely Case
Application crash causing denial of service in affected Moddable-based applications
If Mitigated
No impact if input validation prevents triggering the vulnerable code path
🎯 Exploit Status
Exploitation requires crafting specific input to trigger the buffer overflow; proof-of-concept available in GitHub issue
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: v10.5.1 and later
Vendor Advisory: https://github.com/Moddable-OpenSource/moddable/issues/583
Restart Required: Yes
Instructions:
1. Update Moddable SDK to v10.5.1 or later
2. Rebuild and redeploy all applications using the SDK
3. Test applications for compatibility
🔧 Temporary Workarounds
Input validation
allImplement strict input validation for data passed to fxIDToString function
Memory protection
allEnable ASLR and other memory protection mechanisms on supported platforms
🧯 If You Can't Patch
- Isolate affected applications in network segments with limited access
- Implement strict input filtering and validation for all external data sources
🔍 How to Verify
Check if Vulnerable:
Check if application uses Moddable SDK v10.5.0 and calls fxIDToString with untrusted inputCheck Version:
Check package.json or build configuration for Moddable SDK versionVerify Fix Applied:
Verify Moddable SDK version is v10.5.1 or later and rebuild applications📡 Detection & Monitoring
Log Indicators:
- Application crashes with segmentation faults
- Memory corruption errors in system logs
Network Indicators:
- Unusual traffic patterns to embedded/IoT devices
- Exploit attempts targeting specific application endpoints
SIEM Query:
Process crashes with 'segmentation fault' OR 'heap corruption' AND process_name contains 'moddable'