CVE-2024-46564
📋 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 sProfileName parameter in fextobj.cgi. This affects organizations using Draytek Vigor 3910 routers with vulnerable firmware versions. 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 buffer overflow can be leveraged beyond DoS.
Likely Case
Router becomes unresponsive, requiring manual reboot and causing temporary network disruption for connected users and services.
If Mitigated
If properly segmented and monitored, impact is limited to isolated network segment with quick detection and recovery.
🎯 Exploit Status
The vulnerability is in a CGI parameter, suggesting straightforward exploitation via HTTP requests. No authentication required based on description.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: Not available
Restart Required: Yes
Instructions:
1. Check Draytek's official website for security advisories. 2. Download latest firmware if available. 3. Backup current configuration. 4. Upload and install new firmware via web interface. 5. Reboot router. 6. Restore configuration if needed.
🔧 Temporary Workarounds
Restrict web interface access
allLimit access to the router's web management interface to trusted IP addresses only.
Configure firewall rules to allow only specific source IPs to port 80/443
Disable web interface if not needed
allTemporarily disable the web management interface if remote administration isn't required.
Disable HTTP/HTTPS management in router settings
🧯 If You Can't Patch
- Segment the router on isolated network VLAN to limit blast radius if exploited.
- Implement network monitoring for abnormal HTTP requests to fextobj.cgi with large parameter values.
🔍 How to Verify
Check if Vulnerable:
Check router firmware version in web interface under System Maintenance > Firmware Information.Check Version:
Not applicable - check via web interface or SSH if enabledVerify Fix Applied:
Verify firmware version is updated beyond v4.3.2.6 and test web interface functionality.📡 Detection & Monitoring
Log Indicators:
- HTTP requests to /cgi-bin/fextobj.cgi with unusually long sProfileName parameter
- Router crash/reboot logs
- Failed web interface access attempts
Network Indicators:
- Abnormal HTTP POST requests to router IP on port 80/443 with large payloads
- Sudden loss of router responsiveness
SIEM Query:
source="router_logs" AND (uri="/cgi-bin/fextobj.cgi" AND param_length>100) OR event="router_reboot"