CVE-2023-37793
📋 TL;DR
CVE-2023-37793 is a critical buffer overflow vulnerability in WAYOS FBM-291W routers that allows remote attackers to execute arbitrary code or cause denial of service via the /upgrade_filter.asp component. This affects organizations and individuals using these specific routers with vulnerable firmware. Attackers can exploit this without authentication to gain complete control of affected devices.
💻 Affected Systems
- WAYOS FBM-291W
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete device compromise, lateral movement to internal networks, persistent backdoor installation, and data exfiltration.
Likely Case
Router compromise allowing traffic interception, credential theft, network disruption, and use as botnet node.
If Mitigated
Limited to denial of service if exploit fails or device crashes before code execution.
🎯 Exploit Status
Public proof-of-concept exists in GitHub repository. Exploitation requires sending crafted HTTP request to vulnerable endpoint.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: Not available
Restart Required: Yes
Instructions:
1. Check vendor website for firmware updates. 2. If update available, download and verify checksum. 3. Access router admin interface. 4. Navigate to firmware upgrade section. 5. Upload new firmware file. 6. Wait for reboot and verify version.
🔧 Temporary Workarounds
Disable Web Interface Access
linuxBlock external access to router web management interface
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -j DROP
Network Segmentation
allIsolate vulnerable routers in separate VLAN with restricted access
🧯 If You Can't Patch
- Replace vulnerable devices with supported models
- Implement strict network ACLs to limit access to router management interface
🔍 How to Verify
Check if Vulnerable:
Check firmware version via router web interface or SSH: cat /proc/version or check admin panel system infoCheck Version:
curl -s http://router-ip/ | grep -i version or login to admin interfaceVerify Fix Applied:
Verify firmware version is no longer 19.09.11V and test /upgrade_filter.asp endpoint with controlled payload📡 Detection & Monitoring
Log Indicators:
- Unusual POST requests to /upgrade_filter.asp
- Large payloads in HTTP requests
- Router reboot logs without user action
Network Indicators:
- HTTP requests with oversized parameters to upgrade_filter.asp
- Unusual outbound connections from router
SIEM Query:
source="router_logs" AND (uri="/upgrade_filter.asp" AND content_length>1000)