CVE-2024-42645
📋 TL;DR
An assertion failure vulnerability in FlashMQ v1.14.0 allows attackers to cause a Denial of Service (DoS) by sending a specially crafted retain message. This affects FlashMQ MQTT broker deployments running the vulnerable version, potentially disrupting MQTT messaging services.
💻 Affected Systems
- FlashMQ
📦 What is this software?
Flashmq by Flashmq
⚠️ Risk & Real-World Impact
Worst Case
Complete service outage of FlashMQ broker, disrupting all MQTT communications and potentially affecting dependent IoT/automation systems.
Likely Case
Service crash requiring manual restart, causing temporary disruption to MQTT messaging until service is restored.
If Mitigated
Minimal impact with proper network segmentation and monitoring allowing quick detection and recovery.
🎯 Exploit Status
Exploit requires sending a crafted MQTT retain message, which is trivial for attackers with network access to the broker.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: v1.15.1
Vendor Advisory: https://www.flashmq.org/2024/06/17/flashmq-1-15-1-released/
Restart Required: Yes
Instructions:
1. Download FlashMQ v1.15.1 from official repository. 2. Stop FlashMQ service. 3. Replace binary with patched version. 4. Restart FlashMQ service.
🔧 Temporary Workarounds
Network Access Restriction
linuxRestrict MQTT broker access to trusted networks only
iptables -A INPUT -p tcp --dport 1883 -s trusted_network -j ACCEPT
iptables -A INPUT -p tcp --dport 1883 -j DROP
Downgrade to v1.13.x
linuxRevert to previous stable version if immediate patching isn't possible
wget https://github.com/halfgaar/FlashMQ/releases/tag/v1.13.0
tar -xzf flashmq-1.13.0.tar.gz
cd flashmq-1.13.0 && make && sudo make install
🧯 If You Can't Patch
- Implement strict network segmentation to isolate FlashMQ from untrusted networks
- Deploy rate limiting on MQTT port 1883 to limit attack impact
🔍 How to Verify
Check if Vulnerable:
Check FlashMQ version: ./flashmq --version should show 1.14.0Check Version:
./flashmq --versionVerify Fix Applied:
Verify version is 1.15.1 or higher: ./flashmq --version📡 Detection & Monitoring
Log Indicators:
- Assertion failure messages in FlashMQ logs
- Unexpected service termination/crash logs
- Abnormal retain message patterns
Network Indicators:
- Unusual MQTT retain message traffic from untrusted sources
- Multiple connection attempts with retain flags
SIEM Query:
source="flashmq.log" AND ("assertion" OR "crash" OR "terminated")