CVE-2021-47752
📋 TL;DR
CVE-2021-47752 is a denial of service vulnerability in AWebServer GhostBuilding 18 that allows remote attackers to crash or render the server unresponsive by sending multiple concurrent HTTP requests. This affects systems running the vulnerable version of AWebServer GhostBuilding, particularly those exposed to untrusted networks.
💻 Affected Systems
- AWebServer GhostBuilding
📦 What is this software?
Awebserver by Sylkat Tools
⚠️ Risk & Real-World Impact
Worst Case
Complete service outage with server crash requiring manual restart, potentially leading to extended downtime and business disruption.
Likely Case
Service degradation or temporary unresponsiveness affecting legitimate users until attack traffic subsides.
If Mitigated
Minimal impact with proper rate limiting and monitoring in place to detect and block attack traffic.
🎯 Exploit Status
Exploit code is publicly available on Exploit-DB (ID 50629), making this easily weaponizable by attackers with basic skills.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: http://sylkat-tools.rf.gd/awebserver.htm
Restart Required: No
Instructions:
No official patch identified. Check vendor website for updates and consider upgrading to a newer version if available.
🔧 Temporary Workarounds
Implement Rate Limiting
allConfigure network devices or web application firewalls to limit concurrent connections and request rates per IP address.
Restrict Access
allLimit server exposure by placing behind firewall rules that restrict access to trusted IP addresses only.
🧯 If You Can't Patch
- Deploy a reverse proxy with DoS protection capabilities (like nginx with rate limiting or Cloudflare)
- Monitor server performance metrics and set alerts for abnormal request patterns or resource exhaustion
🔍 How to Verify
Check if Vulnerable:
Check if running AWebServer GhostBuilding version 18. Review application logs for patterns of high concurrent requests from single sources.Check Version:
Check application settings or about page within the AWebServer GhostBuilding app interface.Verify Fix Applied:
Test with controlled concurrent request bursts to verify service remains responsive. Monitor for crash events.📡 Detection & Monitoring
Log Indicators:
- Sudden spikes in concurrent connections
- Multiple rapid requests to /mysqladmin or other endpoints
- Server crash or restart logs
Network Indicators:
- High volume of HTTP requests from single IPs
- Abnormal request patterns with concurrent connections exceeding normal baseline
SIEM Query:
source="webserver_logs" | stats count by src_ip, uri | where count > 1000 | sort -count