CVE-2020-17406
📋 TL;DR
This vulnerability allows authenticated remote attackers to execute arbitrary code as root on Microhard Bullet-LTE devices. The flaw exists in the tools.sh script where user input to the ping parameter is not properly sanitized before being used in a system call. Affected installations are those running Microhard Bullet-LTE firmware prior to version 1.2.0-r1112.
💻 Affected Systems
- Microhard Bullet-LTE
📦 What is this software?
Bullet Lte Firmware by Microhardcorp
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise with root-level code execution, allowing attackers to install persistent backdoors, exfiltrate data, or pivot to other network segments.
Likely Case
Privilege escalation from authenticated user to root, enabling complete control over the device and potential lateral movement within the network.
If Mitigated
Limited impact if proper network segmentation and authentication controls prevent unauthorized access to the vulnerable interface.
🎯 Exploit Status
Exploitation requires authentication but is straightforward once authenticated. The vulnerability is well-documented in ZDI advisories.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: v1.2.0-r1112
Vendor Advisory: https://www.zerodayinitiative.com/advisories/ZDI-20-1205/
Restart Required: Yes
Instructions:
1. Download firmware version 1.2.0-r1112 or later from Microhard. 2. Log into the device web interface. 3. Navigate to System > Firmware Upgrade. 4. Upload the new firmware file. 5. Wait for the upgrade to complete and device to reboot.
🔧 Temporary Workarounds
Disable vulnerable script
linuxRemove execute permissions from the vulnerable tools.sh script to prevent exploitation
chmod -x /path/to/tools.sh
Network segmentation
allIsolate Microhard devices in separate VLANs with strict firewall rules
🧯 If You Can't Patch
- Implement strict access controls to limit who can authenticate to the device
- Monitor for unusual authentication attempts and command execution patterns
🔍 How to Verify
Check if Vulnerable:
Check firmware version via web interface or SSH: cat /etc/versionCheck Version:
cat /etc/versionVerify Fix Applied:
Verify firmware version is 1.2.0-r1112 or later: cat /etc/version | grep -E '1\.2\.0-r1112|^[2-9]|^1\.[3-9]'📡 Detection & Monitoring
Log Indicators:
- Unusual ping commands with shell metacharacters
- Multiple failed authentication attempts followed by successful login
Network Indicators:
- Unusual outbound connections from Microhard devices
- Traffic to unexpected ports
SIEM Query:
source="microhard" AND (event="authentication" OR event="command_execution") AND command="*ping*" AND command="*;*" OR command="*|*" OR command="*&*"