CVE-2021-21748
📋 TL;DR
CVE-2021-21748 affects ZTE MF971R mobile hotspot devices with two stack-based buffer overflow vulnerabilities. Attackers can exploit these vulnerabilities to execute arbitrary code on affected devices. This impacts organizations and individuals using these specific ZTE mobile hotspot products.
💻 Affected Systems
- ZTE MF971R mobile hotspot/router
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise allowing attacker to install persistent malware, intercept all network traffic, pivot to internal networks, and use device as botnet node.
Likely Case
Device takeover leading to credential theft, man-in-the-middle attacks, and unauthorized network access.
If Mitigated
Limited impact if device is isolated, regularly monitored, and has strict network segmentation.
🎯 Exploit Status
Buffer overflow vulnerabilities typically require some technical expertise but are well-understood attack vectors.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check ZTE support for latest firmware
Vendor Advisory: https://support.zte.com.cn/support/news/LoopholeInfoDetail.aspx?newsId=1019764
Restart Required: Yes
Instructions:
1. Visit ZTE support portal 2. Download latest firmware for MF971R 3. Log into device web interface 4. Navigate to firmware update section 5. Upload and apply new firmware 6. Reboot device
🔧 Temporary Workarounds
Disable remote management
allDisable web management interface from WAN/Internet access
Network segmentation
allPlace device in isolated network segment with strict firewall rules
🧯 If You Can't Patch
- Replace vulnerable device with patched or alternative model
- Implement strict network access controls and monitor device traffic for anomalies
🔍 How to Verify
Check if Vulnerable:
Check device firmware version via web interface at 192.168.0.1 or 192.168.1.1Check Version:
Check web interface System Status or About page for firmware versionVerify Fix Applied:
Verify firmware version matches latest patched version from ZTE advisory📡 Detection & Monitoring
Log Indicators:
- Unusual login attempts to web interface
- Multiple buffer overflow attempts in logs
- Unexpected firmware modification
Network Indicators:
- Unusual outbound connections from device
- Port scanning originating from device
- Traffic patterns inconsistent with normal hotspot usage
SIEM Query:
source="zte-mf971r" AND (event="buffer_overflow" OR event="authentication_failure" OR event="firmware_change")