CVE-2024-46593
📋 TL;DR
A buffer overflow vulnerability in Draytek Vigor 3910 routers allows attackers to cause Denial of Service (DoS) by sending crafted input to the trapcomm parameter in cgiswm.cgi. This affects organizations using Draytek Vigor 3910 routers with vulnerable firmware. The vulnerability can disrupt network services by crashing the router.
💻 Affected Systems
- Draytek Vigor 3910
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete router crash requiring physical reboot, extended network downtime, and potential for remote code execution if the overflow can be controlled precisely.
Likely Case
Router becomes unresponsive, requiring manual reboot and causing temporary network disruption for connected users and services.
If Mitigated
Minimal impact if the router is behind a firewall blocking external CGI access, with only authenticated internal users potentially triggering the issue.
🎯 Exploit Status
The vulnerability requires access to the web management interface. Attack complexity is low once access is obtained.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: Not available
Restart Required: Yes
Instructions:
1. Check Draytek website for firmware updates. 2. Download latest firmware. 3. Backup current configuration. 4. Upload and apply new firmware via web interface. 5. Reboot router. 6. Restore configuration if needed.
🔧 Temporary Workarounds
Restrict CGI Access
linuxBlock external access to cgiswm.cgi via firewall rules
iptables -A INPUT -p tcp --dport 80 -m string --string "cgiswm.cgi" --algo bm -j DROP
iptables -A INPUT -p tcp --dport 443 -m string --string "cgiswm.cgi" --algo bm -j DROP
Disable Unused Services
allDisable SNMP trap service if not required
🧯 If You Can't Patch
- Place router behind a firewall that blocks all external access to management interfaces
- Implement network segmentation to isolate the router from untrusted networks
🔍 How to Verify
Check if Vulnerable:
Check firmware version via web interface: System Maintenance > Firmware Information. If version is exactly 4.3.2.6, system is vulnerable.Check Version:
curl -k https://[router-ip]/cgi-bin/mainfunction.cgi?action=login | grep firmwareVerify Fix Applied:
After updating, verify firmware version is different from 4.3.2.6. Test by attempting to access cgiswm.cgi with normal parameters.📡 Detection & Monitoring
Log Indicators:
- Multiple failed CGI requests
- Router reboot events without scheduled maintenance
- Unusual traffic patterns to cgiswm.cgi
Network Indicators:
- HTTP POST requests to /cgi-bin/cgiswm.cgi with unusually long trapcomm parameters
- Sudden drop in router responsiveness
SIEM Query:
source="router_logs" AND (uri="/cgi-bin/cgiswm.cgi" OR message="buffer overflow" OR message="segmentation fault")