CVE-2025-28256
📋 TL;DR
This vulnerability allows remote attackers to execute arbitrary code on TOTOLINK A3100R routers by exploiting improper input sanitization in the setWebWlanIdx function. Attackers can gain full control of affected devices without authentication. Only TOTOLINK A3100R routers running specific vulnerable firmware are affected.
💻 Affected Systems
- TOTOLINK A3100R
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of router with persistent backdoor installation, credential theft, network traffic interception, and lateral movement to connected devices.
Likely Case
Router takeover leading to DNS hijacking, credential harvesting, and use as botnet node for DDoS attacks.
If Mitigated
Limited impact if device is behind firewall with restricted WAN access and network segmentation.
🎯 Exploit Status
Proof-of-concept exploit code is publicly available in GitHub repository. Exploitation requires sending crafted HTTP request to vulnerable endpoint.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: None available
Restart Required: No
Instructions:
No official patch available. Check TOTOLINK website for firmware updates. If update exists, download from official source and flash via web interface.
🔧 Temporary Workarounds
Block Web Interface Access
linuxRestrict access to router web interface from untrusted networks
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 features in router settings
🧯 If You Can't Patch
- Place router behind firewall with strict inbound rules blocking all WAN access to management interfaces
- Implement network segmentation to isolate router from critical internal systems
🔍 How to Verify
Check if Vulnerable:
Check firmware version in router web interface under System Status or Administration settingsCheck Version:
curl -s http://router-ip/cgi-bin/luci/ | grep -i versionVerify Fix Applied:
Verify firmware version is different from V4.1.2cu.5247_B20211129📡 Detection & Monitoring
Log Indicators:
- Unusual POST requests to /cgi-bin/luci
- Multiple failed authentication attempts followed by successful access
- Unexpected process execution in system logs
Network Indicators:
- HTTP requests containing shell commands or encoded payloads to router IP
- Outbound connections from router to unknown IPs
SIEM Query:
source="router.log" AND ("setWebWlanIdx" OR "/cgi-bin/luci" AND status=200)