CVE-2023-33637
📋 TL;DR
This vulnerability allows remote attackers to execute arbitrary code on H3C Magic R300 routers via a stack overflow in the DelDNSHnList interface. Attackers can exploit this by sending specially crafted requests to the /goform/aspForm endpoint. Only users of specific H3C Magic R300 router versions are affected.
💻 Affected Systems
- H3C Magic R300
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise leading to complete router takeover, credential theft, network traffic interception, and lateral movement into connected networks.
Likely Case
Router compromise allowing attackers to modify DNS settings, intercept traffic, deploy malware to connected devices, or create persistent backdoors.
If Mitigated
Limited impact with proper network segmentation and access controls, potentially only affecting the router's management interface.
🎯 Exploit Status
Public proof-of-concept exists showing exploitation details. The vulnerability requires no authentication and has straightforward exploitation.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: Not publicly available
Restart Required: Yes
Instructions:
1. Check H3C official website for firmware updates
2. Download latest firmware for R300
3. Access router web interface
4. Navigate to firmware upgrade section
5. Upload and apply new firmware
6. Reboot router after update
🔧 Temporary Workarounds
Disable Web Management Interface
allDisable the vulnerable web interface to prevent exploitation
Access router CLI via SSH/Telnet
Enter configuration mode
Disable web management service
Network Access Control
allRestrict access to router management interface
Configure firewall rules to block external access to port 80/443
Implement IP whitelisting for management access
🧯 If You Can't Patch
- Isolate affected routers in separate VLAN with strict access controls
- Implement network monitoring for suspicious requests to /goform/aspForm endpoint
🔍 How to Verify
Check if Vulnerable:
Check router firmware version via web interface at System Status > Firmware VersionCheck Version:
curl -s http://router-ip/status.asp | grep FirmwareVerify Fix Applied:
Verify firmware version has been updated to a version later than R300-2100MV100R004📡 Detection & Monitoring
Log Indicators:
- Multiple POST requests to /goform/aspForm with abnormal payload sizes
- Router reboot events following suspicious requests
- DNS configuration changes without administrator action
Network Indicators:
- Unusual outbound connections from router to unknown IPs
- DNS queries to suspicious domains
- Traffic patterns indicating router compromise
SIEM Query:
source="router_logs" AND (uri="/goform/aspForm" AND content_length>1000) OR event="firmware_change"