CVE-2021-28151
📋 TL;DR
This vulnerability allows remote attackers to execute arbitrary operating system commands on Hongdian H8922 devices by injecting shell metacharacters into the Destination field of the ping command in tools.cgi. Attackers can exploit this using the default guest credentials (username: guest, password: guest). All organizations using Hongdian H8922 version 3.0.5 devices are affected.
💻 Affected Systems
- Hongdian H8922
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise leading to network pivoting, data exfiltration, or deployment of persistent malware across connected systems.
Likely Case
Unauthorized command execution allowing attackers to modify device configuration, disrupt network services, or use the device as a foothold for further attacks.
If Mitigated
Limited impact if proper network segmentation and access controls prevent exploitation attempts.
🎯 Exploit Status
Exploitation requires authentication with guest credentials, which are default and commonly unchanged. The vulnerability is straightforward to exploit once authenticated.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: http://en.hongdian.com/Products/Details/H8922
Restart Required: No
Instructions:
No official patch available. Contact Hongdian support for updated firmware. If unavailable, implement workarounds and compensating controls.
🔧 Temporary Workarounds
Change Default Credentials
allChange the default guest password to a strong, unique password to prevent unauthorized access.
Login to device web interface > System > User Management > Change guest password
Disable Guest Account
allDisable or remove the guest account entirely if not needed for operations.
Login to device web interface > System > User Management > Disable/Delete guest account
Restrict Network Access
linuxUse firewall rules to restrict access to the device management interface to trusted IP addresses only.
iptables -A INPUT -p tcp --dport 80 -s trusted_ip -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
🧯 If You Can't Patch
- Implement strict network segmentation to isolate Hongdian H8922 devices from critical systems
- Deploy intrusion detection systems to monitor for command injection attempts and unusual network traffic
🔍 How to Verify
Check if Vulnerable:
Attempt to access the tools.cgi interface with guest/guest credentials and test command injection in the Destination field. Monitor device logs for unauthorized access attempts.Check Version:
Check device web interface > System > Device Information for firmware versionVerify Fix Applied:
Verify that guest credentials no longer work or have been changed. Test that command injection attempts are blocked or logged.📡 Detection & Monitoring
Log Indicators:
- Failed login attempts to guest account
- Unusual commands in system logs
- Access to tools.cgi from unauthorized sources
Network Indicators:
- Unusual outbound connections from the device
- Traffic patterns indicating command and control activity
- HTTP requests to tools.cgi with shell metacharacters
SIEM Query:
source="hongdian_device" AND (url="*/tools.cgi*" AND (param="*;*" OR param="*|*" OR param="*`*"))