CVE-2020-17407
📋 TL;DR
CVE-2020-17407 is a critical buffer overflow vulnerability in Microhard Bullet-LTE devices that allows unauthenticated remote attackers to execute arbitrary code as root. The vulnerability exists in authentication header handling where user-supplied data isn't properly validated before being copied to a fixed-length buffer. All installations prior to version 1.2.0-r1112 are affected.
💻 Affected Systems
- Microhard Bullet-LTE
📦 What is this software?
Bullet Lte Firmware by Microhardcorp
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with root-level code execution, allowing attackers to install persistent backdoors, pivot to internal networks, or render devices inoperable.
Likely Case
Remote code execution leading to device takeover, credential theft, and use as a foothold for lateral movement within networks.
If Mitigated
Attackers can still crash services but cannot execute arbitrary code if proper memory protections are enabled.
🎯 Exploit Status
The ZDI advisory suggests reliable exploitation is straightforward given the buffer overflow nature and root execution context.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 1.2.0-r1112
Vendor Advisory: https://www.zerodayinitiative.com/advisories/ZDI-20-1206/
Restart Required: Yes
Instructions:
1. Download firmware version 1.2.0-r1112 or later from Microhard. 2. Backup current configuration. 3. Upload new firmware via web interface. 4. Apply configuration backup. 5. Reboot device.
🔧 Temporary Workarounds
Network Segmentation
allIsolate Microhard devices in separate VLANs with strict firewall rules limiting access to management interfaces.
Access Control Lists
allImplement IP-based restrictions to only allow trusted management stations to access device interfaces.
🧯 If You Can't Patch
- Immediately remove devices from internet-facing deployments and place behind VPNs with strict access controls.
- Implement network-based intrusion prevention systems (IPS) with rules to detect and block exploitation attempts.
🔍 How to Verify
Check if Vulnerable:
Check firmware version via web interface or SSH: cat /etc/version or similar version file.Check Version:
cat /etc/version || cat /proc/version || grep -i version /etc/*releaseVerify Fix Applied:
Confirm firmware version is 1.2.0-r1112 or higher using the same version check command.📡 Detection & Monitoring
Log Indicators:
- Multiple failed authentication attempts with malformed headers
- Process crashes in authentication service
- Unusual root-level process execution
Network Indicators:
- Unusual traffic patterns to/from Microhard devices
- Exploit-specific payloads in HTTP headers
- Sudden device reboots or service restarts
SIEM Query:
source="microhard" AND (event="authentication_failure" OR event="service_crash") AND header_length>threshold