CVE-2021-46020
📋 TL;DR
This vulnerability involves an untrusted pointer dereference in mruby's virtual machine execution function, which can cause a segmentation fault and crash the application. It affects systems running mruby 3.0.0, potentially impacting any application or service using this Ruby implementation.
💻 Affected Systems
- mruby
📦 What is this software?
Mruby by Mruby
⚠️ Risk & Real-World Impact
Worst Case
Denial of service leading to application unavailability, potentially enabling further exploitation if combined with other vulnerabilities.
Likely Case
Application crash resulting in service disruption and potential data loss in active transactions.
If Mitigated
Limited impact with proper isolation and monitoring, though service disruption remains possible.
🎯 Exploit Status
The vulnerability is triggered through crafted mruby bytecode, making exploitation straightforward for attackers with code execution capability.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: mruby 3.0.1 or later
Vendor Advisory: https://github.com/mruby/mruby/issues/5613
Restart Required: Yes
Instructions:
1. Update mruby to version 3.0.1 or later. 2. Recompile any applications using mruby. 3. Restart affected services.
🔧 Temporary Workarounds
Input validation and sanitization
allImplement strict validation of mruby bytecode inputs to prevent malicious code execution.
🧯 If You Can't Patch
- Isolate mruby applications in containers or sandboxes to limit blast radius
- Implement rate limiting and monitoring for abnormal application crashes
🔍 How to Verify
Check if Vulnerable:
Check mruby version with 'mruby --version' or examine application dependencies for mruby 3.0.0Check Version:
mruby --versionVerify Fix Applied:
Confirm mruby version is 3.0.1 or later and test application functionality📡 Detection & Monitoring
Log Indicators:
- Segmentation fault errors in application logs
- Unexpected application termination
Network Indicators:
- Sudden service unavailability
- Connection resets
SIEM Query:
source="application.logs" AND ("segmentation fault" OR "SIGSEGV")