CVE-2021-26195
📋 TL;DR
CVE-2021-26195 is a heap buffer overflow vulnerability in JerryScript's number parsing function that allows attackers to execute arbitrary code or cause denial of service. This affects applications using JerryScript 2.4.0 for JavaScript execution, particularly IoT devices and embedded systems. Attackers can exploit this by providing malicious JavaScript input to vulnerable systems.
💻 Affected Systems
- JerryScript
📦 What is this software?
Jerryscript by Jerryscript
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise, data theft, or device takeover
Likely Case
Denial of service causing application crashes and service disruption
If Mitigated
Contained crash with minimal impact if proper memory protections and sandboxing are implemented
🎯 Exploit Status
Proof of concept available in GitHub issues; exploitation requires ability to supply JavaScript input to vulnerable parser
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2.4.1 and later
Vendor Advisory: https://github.com/jerryscript-project/jerryscript/issues/4442
Restart Required: Yes
Instructions:
1. Update JerryScript to version 2.4.1 or later. 2. Recompile applications using JerryScript. 3. Restart affected services.
🔧 Temporary Workarounds
Input Validation
allImplement strict input validation to reject malformed JavaScript before it reaches the parser
Memory Protection
linuxEnable ASLR and DEP/PaX to make exploitation more difficult
echo 2 > /proc/sys/kernel/randomize_va_space
🧯 If You Can't Patch
- Isolate JerryScript instances in containers with minimal privileges
- Implement network segmentation to limit access to vulnerable systems
🔍 How to Verify
Check if Vulnerable:
Check JerryScript version: jerry --version should show 2.4.0 if vulnerableCheck Version:
jerry --versionVerify Fix Applied:
Verify version is 2.4.1 or later: jerry --version📡 Detection & Monitoring
Log Indicators:
- Segmentation fault logs
- Memory access violation errors
- Unexpected JerryScript process termination
Network Indicators:
- Unusual JavaScript payloads in network traffic
- Repeated connection attempts to JerryScript services
SIEM Query:
process_name:"jerry" AND (event_type:"crash" OR exit_code:139)