CVE-2024-46566
📋 TL;DR
A buffer overflow vulnerability exists in the sAppName parameter of the sslapp.cgi component in Draytek Vigor 3910 firmware v4.3.2.6. Attackers can exploit this by sending crafted inputs to cause a Denial of Service (DoS), potentially crashing the device. This affects all users running the vulnerable firmware version on Draytek Vigor 3910 routers.
💻 Affected Systems
- Draytek Vigor 3910
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device crash requiring physical reboot, potential remote code execution if buffer overflow can be controlled precisely (though not indicated in description), and extended network downtime.
Likely Case
Denial of Service causing router reboot and temporary network interruption for connected users and services.
If Mitigated
Minimal impact if device is behind firewall with restricted access to management interface and proper network segmentation.
🎯 Exploit Status
Based on CVE description, exploitation appears straightforward via crafted HTTP request to vulnerable endpoint.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: Not available in provided references
Restart Required: Yes
Instructions:
1. Check Draytek official website for firmware updates. 2. Download latest firmware for Vigor 3910. 3. Backup current configuration. 4. Upload new firmware via web interface. 5. Reboot device after update completes.
🔧 Temporary Workarounds
Restrict Access to Management Interface
allLimit access to the router's web management interface to trusted IP addresses only.
Configure firewall rules to allow only specific source IPs to access port 80/443 on the router
Disable Unnecessary Services
allDisable remote management if not required.
Navigate to Management > Access Control > Remote Management in web interface and disable
🧯 If You Can't Patch
- Implement strict network segmentation to isolate the router from untrusted networks
- Deploy intrusion prevention system (IPS) with rules to detect buffer overflow attempts against sslapp.cgi
🔍 How to Verify
Check if Vulnerable:
Check firmware version in web interface under Maintenance > System Status > Firmware InformationCheck Version:
curl -k https://[router-ip]/cgi-bin/sslapp.cgi?action=version (if available) or check web interfaceVerify Fix Applied:
Verify firmware version is no longer v4.3.2.6 and test sslapp.cgi endpoint with monitoring for crashes📡 Detection & Monitoring
Log Indicators:
- Repeated connection attempts to sslapp.cgi
- Device reboot logs without normal shutdown
- Large/unusual parameter values in web logs
Network Indicators:
- HTTP POST/GET requests to /cgi-bin/sslapp.cgi with unusually long sAppName parameter
- Sudden loss of connectivity to router management interface
SIEM Query:
source="router_logs" AND (uri="/cgi-bin/sslapp.cgi" AND (param_length>100 OR contains(param_value, suspicious_patterns)))