CVE-2020-15866
📋 TL;DR
CVE-2020-15866 is a critical heap-based buffer overflow vulnerability in mruby's virtual machine stack handling. Attackers can exploit this to execute arbitrary code or cause denial of service. This affects all systems running vulnerable versions of mruby, particularly embedded systems and applications using mruby as a lightweight Ruby implementation.
💻 Affected Systems
- mruby
📦 What is this software?
Mruby by Mruby
Mruby by Mruby
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise, data theft, or ransomware deployment
Likely Case
Denial of service crashes or limited code execution depending on exploit implementation
If Mitigated
Contained impact with proper memory protections and exploit mitigations in place
🎯 Exploit Status
Proof of concept exists in GitHub issues, exploitation requires crafting specific mruby bytecode
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: mruby 2.1.3 and later
Vendor Advisory: https://github.com/mruby/mruby/issues/5042
Restart Required: Yes
Instructions:
1. Update mruby to version 2.1.3 or later. 2. Recompile any applications using mruby. 3. Restart affected services.
🔧 Temporary Workarounds
Memory protection hardening
linuxEnable ASLR, DEP, and other memory protection mechanisms
echo 2 > /proc/sys/kernel/randomize_va_space
sysctl -w kernel.exec-shield=1
🧯 If You Can't Patch
- Network segmentation to isolate mruby systems from untrusted networks
- Implement strict input validation and sandboxing for mruby execution environments
🔍 How to Verify
Check if Vulnerable:
Check mruby version with 'mruby --version' or examine application dependenciesCheck Version:
mruby --versionVerify Fix Applied:
Confirm mruby version is 2.1.3 or higher and test with known exploit payloads📡 Detection & Monitoring
Log Indicators:
- Segmentation fault crashes in mruby processes
- Unusual memory allocation patterns
Network Indicators:
- Unexpected network connections from mruby processes
- Exploit attempt patterns in network traffic
SIEM Query:
process_name:mruby AND (event_type:crash OR memory_usage:spike)