CVE-2021-47752 Overview
CVE-2021-47752 is a denial of service vulnerability affecting AWebServer GhostBuilding version 18, a mobile web server application for Android devices. The vulnerability allows remote attackers to overwhelm the server by sending multiple concurrent HTTP requests, potentially crashing the service or rendering it unresponsive. Attackers can generate high-volume requests to multiple endpoints including /mysqladmin to exploit this weakness.
Critical Impact
Remote attackers can cause service disruption by flooding the server with concurrent HTTP requests, leading to resource exhaustion and denial of service conditions.
Affected Products
- AWebServer GhostBuilding 18
- AWebServer for Android (com.sylkat.apache)
Discovery Timeline
- 2026-01-15 - CVE CVE-2021-47752 published to NVD
- 2026-01-16 - Last updated in NVD database
Technical Details for CVE-2021-47752
Vulnerability Analysis
This vulnerability is classified under CWE-770 (Allocation of Resources Without Limits or Throttling). The core issue lies in the server's inability to properly manage and limit incoming concurrent HTTP connections. When an attacker initiates a large number of simultaneous HTTP requests, the server fails to implement proper rate limiting or connection throttling mechanisms. This results in resource exhaustion as the server attempts to handle all incoming requests without any protective boundaries.
The attack is particularly effective because it can target multiple endpoints simultaneously, including the /mysqladmin administrative interface, amplifying the impact on system resources.
Root Cause
The root cause of this vulnerability stems from improper resource allocation controls within AWebServer GhostBuilding 18. The server lacks adequate mechanisms to:
- Limit the number of concurrent connections from a single source
- Implement request rate limiting per client
- Manage system resource allocation during high-load scenarios
- Queue or reject excessive requests when approaching resource limits
This absence of resource management controls allows attackers to consume all available server resources through connection flooding.
Attack Vector
The attack is network-based and requires no authentication or user interaction. An attacker can remotely exploit this vulnerability by:
- Identifying a vulnerable AWebServer GhostBuilding 18 instance
- Initiating multiple concurrent HTTP connections to the server
- Targeting various endpoints including the /mysqladmin interface
- Sustaining the high volume of requests to maintain the denial of service condition
The attack can be launched from any network-accessible position, making it particularly dangerous for servers exposed to the internet or untrusted networks. A public exploit is available through Exploit-DB #50629 which demonstrates the concurrent request flooding technique.
Detection Methods for CVE-2021-47752
Indicators of Compromise
- Abnormally high number of concurrent HTTP connections from single or multiple source IPs
- Sudden spike in requests to /mysqladmin or other server endpoints
- Server resource exhaustion indicators including high CPU and memory utilization
- Increased connection timeouts or service unavailability reports
Detection Strategies
- Implement network traffic analysis to identify unusual patterns of concurrent HTTP requests
- Configure web server log monitoring to detect request flooding patterns
- Deploy intrusion detection systems (IDS) with rules for HTTP flood detection
- Monitor for repeated rapid connections from the same source addresses
Monitoring Recommendations
- Set up alerts for connection rate thresholds being exceeded
- Monitor server resource utilization (CPU, memory, network connections) for anomalies
- Implement log aggregation to correlate connection patterns across time periods
- Configure real-time dashboards to visualize incoming connection rates and server health
How to Mitigate CVE-2021-47752
Immediate Actions Required
- Limit network exposure of AWebServer instances to trusted networks only
- Implement network-level rate limiting using firewalls or reverse proxies
- Consider disabling or restricting access to the /mysqladmin endpoint if not required
- Monitor for any signs of active exploitation attempts
Patch Information
No official vendor patch information is currently available for this vulnerability. Users should check the Sylkat Tools Web Server page and the Google Play Store listing for updates and newer versions that may address this vulnerability.
Workarounds
- Deploy a reverse proxy or web application firewall (WAF) in front of AWebServer to implement rate limiting
- Configure network firewall rules to limit the number of connections per source IP
- Restrict access to the server to known and trusted IP addresses only
- Consider using alternative web server software with built-in DoS protection mechanisms
# Example iptables rate limiting configuration
# Limit new HTTP connections to 25 per minute per source IP
iptables -A INPUT -p tcp --dport 80 -m state --state NEW -m recent --set
iptables -A INPUT -p tcp --dport 80 -m state --state NEW -m recent --update --seconds 60 --hitcount 25 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
