CVE-2025-45835
📋 TL;DR
A null pointer dereference vulnerability in Netis WF2880 routers allows attackers to cause denial-of-service by manipulating the CONTENT_LENGTH environment variable. This affects Netis WF2880 v2.1.40207 routers running the vulnerable cgitest.cgi component. Attackers can crash the service, disrupting router functionality.
💻 Affected Systems
- Netis WF2880
📦 What is this software?
Wf2880 Firmware by Netis Systems
⚠️ Risk & Real-World Impact
Worst Case
Complete router service disruption requiring physical reboot, potentially affecting all connected devices and network services.
Likely Case
Temporary denial-of-service affecting web interface and potentially other router services until automatic restart or manual intervention.
If Mitigated
Minimal impact if router has automatic restart capabilities and network segmentation limits blast radius.
🎯 Exploit Status
Public GitHub repository contains proof-of-concept. Exploitation requires sending specially crafted HTTP requests to the vulnerable endpoint.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: Unknown
Restart Required: Yes
Instructions:
1. Check Netis website for firmware updates
2. Download latest firmware for WF2880
3. Access router admin interface
4. Navigate to firmware upgrade section
5. Upload and apply new firmware
6. Reboot router after update completes
🔧 Temporary Workarounds
Disable cgitest.cgi access
linuxBlock access to the vulnerable CGI component using firewall rules or web server configuration
iptables -A INPUT -p tcp --dport 80 -m string --string "cgitest.cgi" --algo bm -j DROP
iptables -A INPUT -p tcp --dport 443 -m string --string "cgitest.cgi" --algo bm -j DROP
Restrict web interface access
linuxLimit router web interface access 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
iptables -A INPUT -p tcp --dport 443 -s TRUSTED_IP -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP
🧯 If You Can't Patch
- Segment router management interface to isolated VLAN
- Implement network monitoring for DoS attempts against router web interface
🔍 How to Verify
Check if Vulnerable:
Check firmware version in router admin interface under System Status or About page. If version is v2.1.40207, device is vulnerable.Check Version:
curl -s http://router-ip/ | grep -i version || ssh admin@router-ip 'cat /proc/version'Verify Fix Applied:
After firmware update, verify version is no longer v2.1.40207. Test by attempting to access cgitest.cgi endpoint with malformed CONTENT_LENGTH.📡 Detection & Monitoring
Log Indicators:
- Multiple connection attempts to cgitest.cgi endpoint
- Router service crash/restart logs
- Unusual CONTENT_LENGTH values in web logs
Network Indicators:
- HTTP requests with malformed or extremely large CONTENT_LENGTH headers
- Repeated requests to /cgitest.cgi endpoint
SIEM Query:
source="router_logs" AND (uri="/cgitest.cgi" OR user_agent CONTAINS "exploit" OR content_length>1000000)