CVE-2024-46595
📋 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 saveitem parameter in lan2lan.cgi. This affects organizations using Draytek Vigor 3910 routers with vulnerable firmware versions. The vulnerability can disrupt network connectivity and router functionality.
💻 Affected Systems
- Draytek Vigor 3910
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete router crash requiring physical reboot, persistent network downtime, and potential for remote code execution if the buffer overflow can be leveraged beyond DoS.
Likely Case
Router becomes unresponsive, requiring reboot to restore functionality, causing temporary network disruption for connected devices.
If Mitigated
Limited impact with proper network segmentation and access controls preventing exploitation attempts.
🎯 Exploit Status
Buffer overflow vulnerabilities in web interfaces often have low exploitation complexity. The CWE-120 classification indicates classic buffer copy without checking size.
🛠️ 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 if available
3. Backup current configuration
4. Upload and install new firmware via web interface
5. Restart router
6. Restore configuration if needed
🔧 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 restrict access to router management IP on ports 80/443
Disable Unnecessary CGI Functions
allIf possible, disable or restrict access to lan2lan.cgi functionality
Check router configuration for CGI access controls
🧯 If You Can't Patch
- Implement strict network segmentation to isolate the router from untrusted networks
- Deploy network intrusion detection/prevention systems to monitor for exploitation attempts
🔍 How to Verify
Check if Vulnerable:
Check router firmware version via web interface at System Maintenance > Firmware InformationCheck Version:
Not applicable - check via web interfaceVerify Fix Applied:
Verify firmware version is newer than v4.3.2.6 after update📡 Detection & Monitoring
Log Indicators:
- Multiple failed requests to lan2lan.cgi
- Router reboot events
- Unusual traffic patterns to router management interface
Network Indicators:
- HTTP POST requests to /cgi-bin/lan2lan.cgi with large saveitem parameters
- Sudden loss of router responsiveness
SIEM Query:
source="router_logs" AND (uri="/cgi-bin/lan2lan.cgi" OR event="reboot")