CVE-2021-44246
📋 TL;DR
This vulnerability is a stack overflow in the setNoticeCfg function of Totolink routers, allowing attackers to cause Denial of Service (DoS) by sending specially crafted requests with the IpTo parameter. It affects specific Totolink router models running vulnerable firmware versions. Attackers can crash the device, disrupting network services.
💻 Affected Systems
- Totolink A3100R
- Totolink A830R
- Totolink A720R
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device crash requiring physical reboot, extended service disruption, potential for remote code execution if stack overflow can be controlled (though not confirmed).
Likely Case
Temporary DoS causing network outage until device reboots automatically or manually.
If Mitigated
Limited impact if devices are behind firewalls with restricted WAN access and proper network segmentation.
🎯 Exploit Status
Public GitHub repository contains proof-of-concept. Exploitation requires sending crafted HTTP request to vulnerable endpoint.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: None found
Restart Required: No
Instructions:
Check Totolink website for firmware updates. If available, download and flash via web interface.
🔧 Temporary Workarounds
Restrict Management Interface Access
linuxBlock external access to router management interface using firewall rules.
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -j DROP
Disable Remote Management
allTurn off remote administration in router settings if not needed.
🧯 If You Can't Patch
- Isolate affected routers in separate VLAN with strict access controls.
- Implement network monitoring for abnormal traffic patterns to vulnerable endpoints.
🔍 How to Verify
Check if Vulnerable:
Check router firmware version in web interface. If matches affected versions, assume vulnerable.Check Version:
curl -s http://router-ip/ | grep -i firmwareVerify Fix Applied:
Verify firmware version has been updated to non-vulnerable version.📡 Detection & Monitoring
Log Indicators:
- Multiple connection attempts to /cgi-bin/setNoticeCfg endpoint
- Device reboot logs after network traffic
Network Indicators:
- HTTP POST requests to /cgi-bin/setNoticeCfg with long IpTo parameter
- Unusual traffic from external IPs to router management ports
SIEM Query:
source="router.log" AND "setNoticeCfg" AND ("IpTo=" OR "POST /cgi-bin/")