CVE-2024-46550
📋 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 CGIbyFieldName parameter in chglog.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 until service is restored.
If Mitigated
Minimal impact if the router is behind proper network segmentation and firewalls, with monitoring to detect exploitation attempts.
🎯 Exploit Status
The vulnerability is in a CGI parameter accessible via HTTP, making exploitation straightforward if the router is exposed.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: Not available
Restart Required: Yes
Instructions:
1. Check Draytek's official website or support for firmware updates. 2. Download the latest firmware if available. 3. Upload and apply the firmware via the router's web interface. 4. Reboot the router to complete the update.
🔧 Temporary Workarounds
Block External Access to chglog.cgi
linuxUse firewall rules to block incoming HTTP requests to the chglog.cgi endpoint on the router.
iptables -A INPUT -p tcp --dport 80 -m string --string "chglog.cgi" --algo bm -j DROP
iptables -A INPUT -p tcp --dport 443 -m string --string "chglog.cgi" --algo bm -j DROP
🧯 If You Can't Patch
- Isolate the router on a dedicated network segment to limit exposure.
- Implement strict network access controls to allow only trusted IPs to access the router's management interface.
🔍 How to Verify
Check if Vulnerable:
Check the router's firmware version via the web interface under System Maintenance > Firmware Information.Check Version:
curl -s http://router-ip/cgi-bin/chglog.cgi | grep -i versionVerify Fix Applied:
Verify the firmware version has been updated to a version later than v4.3.2.6, if a patch is released.📡 Detection & Monitoring
Log Indicators:
- Unusual HTTP POST requests to chglog.cgi with long parameter values
- Router crash logs or reboots in system logs
Network Indicators:
- HTTP traffic to router IP on port 80/443 with requests containing CGIbyFieldName parameter exceeding normal length
SIEM Query:
source="router_logs" AND (uri="*chglog.cgi*" AND (param="*CGIbyFieldName*" AND length>100))