CVE-2020-29657
📋 TL;DR
CVE-2020-29657 is an out-of-bounds read vulnerability in JerryScript 2.3.0's main-utils.c file that could allow attackers to read sensitive memory contents or cause denial of service. This affects systems using JerryScript, a lightweight JavaScript engine for embedded devices. The vulnerability is particularly concerning for IoT devices and embedded systems running vulnerable JerryScript versions.
💻 Affected Systems
- JerryScript
📦 What is this software?
Jerryscript by Jerryscript
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise, memory disclosure of sensitive data, or persistent denial of service.
Likely Case
Application crash causing denial of service, potential information disclosure through memory reads.
If Mitigated
Controlled crash with minimal impact if proper memory protections and sandboxing are implemented.
🎯 Exploit Status
The vulnerability is in the main_print_unhandled_exception function which handles exceptions, making it accessible during normal script execution. Proof of concept exists in the GitHub issue.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: JerryScript 2.4.0 and later
Vendor Advisory: https://github.com/jerryscript-project/jerryscript/issues/4244
Restart Required: Yes
Instructions:
1. Update JerryScript to version 2.4.0 or later. 2. Recompile any applications using JerryScript. 3. Restart affected services or devices.
🔧 Temporary Workarounds
Disable exception printing
allModify code to avoid calling main_print_unhandled_exception function
Modify main-utils.c to remove or bypass the vulnerable function call
Memory protection hardening
linuxEnable ASLR and other memory protection mechanisms
echo 2 > /proc/sys/kernel/randomize_va_space
Enable DEP/NX bit if available
🧯 If You Can't Patch
- Network segmentation: Isolate devices running vulnerable JerryScript versions
- Implement strict input validation and sandboxing for JavaScript execution
🔍 How to Verify
Check if Vulnerable:
Check JerryScript version: jerry --version should show 2.3.0 if vulnerableCheck Version:
jerry --versionVerify Fix Applied:
Verify jerry --version shows 2.4.0 or later📡 Detection & Monitoring
Log Indicators:
- Segmentation fault logs
- Memory access violation errors
- JerryScript crash reports
Network Indicators:
- Unexpected traffic from JerryScript devices
- Anomalous memory-related network patterns
SIEM Query:
source="*jerry*" AND ("segmentation fault" OR "out of bounds" OR "memory violation")