CVE-2020-22886
📋 TL;DR
A buffer overflow vulnerability in the jsG_markobject function of mujs JavaScript interpreter allows remote attackers to cause denial of service. This affects systems running vulnerable versions of mujs before 1.0.8. The vulnerability can be triggered through specially crafted JavaScript input.
💻 Affected Systems
- mujs
📦 What is this software?
Mujs by Artifex
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise, though this would require additional exploitation techniques beyond the documented DoS.
Likely Case
Denial of service causing application crashes or instability in systems using mujs for JavaScript processing.
If Mitigated
Limited impact with proper input validation and sandboxing of JavaScript execution environments.
🎯 Exploit Status
Proof of concept available in GitHub issue #134. Exploitation requires ability to supply JavaScript input to mujs.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 1.0.8 and later
Vendor Advisory: https://github.com/ccxvii/mujs/issues/134
Restart Required: Yes
Instructions:
1. Download mujs 1.0.8 or later from official repository. 2. Replace existing mujs installation with patched version. 3. Restart any services or applications using mujs.
🔧 Temporary Workarounds
Input Validation
allImplement strict input validation and sanitization for JavaScript content processed by mujs.
Sandbox Execution
allRun mujs in isolated containers or sandboxed environments to limit impact of potential exploitation.
🧯 If You Can't Patch
- Implement network segmentation to isolate systems running vulnerable mujs versions.
- Deploy application firewalls to filter and monitor JavaScript input to mujs.
🔍 How to Verify
Check if Vulnerable:
Check mujs version with 'mujs --version' or examine installed package version.Check Version:
mujs --versionVerify Fix Applied:
Verify version is 1.0.8 or later and test with known exploit payloads.📡 Detection & Monitoring
Log Indicators:
- Application crashes
- Segmentation faults in mujs processes
- Unusual memory usage patterns
Network Indicators:
- Unusual JavaScript payloads sent to services using mujs
SIEM Query:
Process crashes with mujs in stack trace OR Application logs containing mujs segmentation faults