CVE-2021-26797
📋 TL;DR
This critical vulnerability in Hame SD1 Wi-Fi firmware allows attackers to gain administrator access through an open Telnet service with default credentials. It affects all Hame SD1 Wi-Fi devices running firmware version V.20140224154640 or earlier. Attackers can completely compromise affected devices.
💻 Affected Systems
- Hame SD1 Wi-Fi device
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device takeover allowing attackers to intercept all network traffic, install malware, pivot to other network devices, and maintain persistent access.
Likely Case
Attackers gain full administrative control of the Wi-Fi device, enabling them to monitor network traffic, change device settings, and potentially access connected devices.
If Mitigated
With proper network segmentation and access controls, impact is limited to the compromised device only.
🎯 Exploit Status
Exploitation requires only Telnet access to the device with default credentials. No special tools or skills needed.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: None available
Vendor Advisory: No vendor advisory found
Restart Required: No
Instructions:
No official patch exists. Replace affected devices or implement workarounds.
🔧 Temporary Workarounds
Disable Telnet service
allDisable the Telnet service if the device configuration allows it
Check device admin interface for Telnet disable option
Network access control
linuxBlock Telnet port (23) at network perimeter and internally
iptables -A INPUT -p tcp --dport 23 -j DROP
firewall-cmd --permanent --add-port=23/tcp
firewall-cmd --reject
🧯 If You Can't Patch
- Isolate affected devices in separate VLAN with strict access controls
- Replace affected Hame SD1 devices with secure alternatives
🔍 How to Verify
Check if Vulnerable:
Attempt Telnet connection to device on port 23 with default credentials (admin/admin or similar)Check Version:
Check device web interface or console for firmware versionVerify Fix Applied:
Verify Telnet port 23 is closed or inaccessible, and alternative access methods are secured📡 Detection & Monitoring
Log Indicators:
- Failed/successful Telnet authentication attempts
- Unexpected configuration changes
Network Indicators:
- Telnet connections to device IP on port 23
- Unusual outbound connections from device
SIEM Query:
source_port=23 OR destination_port=23 AND (event_type="authentication" OR event_type="connection")