CVE-2009-5111 in WebServer
Summary
by MITRE
GoAhead WebServer allows remote attackers to cause a denial of service (daemon outage) via partial HTTP requests, as demonstrated by Slowloris.
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Analysis
by VulDB Data Team • 04/10/2017
The vulnerability identified as CVE-2009-5111 affects the GoAhead WebServer implementation and represents a significant denial of service weakness that can be exploited by remote attackers to disrupt web services. This vulnerability specifically manifests through the processing of partial HTTP requests, creating a condition where the web server daemon becomes unresponsive or crashes entirely. The exploitation technique leverages the Slowloris attack pattern, which involves sending partial HTTP requests that are intentionally left incomplete to maintain open connections with the target server. This approach consumes server resources and prevents legitimate requests from being processed, ultimately leading to service disruption.
The technical flaw resides in the web server's handling of incomplete HTTP requests and its lack of proper timeout mechanisms for partial requests. When GoAhead WebServer receives partial HTTP requests, it maintains these connections open indefinitely without implementing adequate resource management or connection timeout controls. This behavior creates a resource exhaustion scenario where the server's connection pool becomes saturated with incomplete requests, preventing it from accepting new legitimate connections. The vulnerability directly maps to CWE-400, which addresses unchecked resource consumption, and specifically relates to the improper handling of network connections and resource management within web server implementations.
From an operational impact perspective, this vulnerability poses a severe threat to web service availability and can result in complete daemon outages that affect business operations and user access. The Slowloris attack pattern is particularly effective because it requires minimal resources to execute while causing maximum disruption, making it a favored technique among attackers seeking to disable web services without triggering obvious network-based detection mechanisms. Organizations running GoAhead WebServer are vulnerable to sustained attacks that can maintain service disruption for extended periods, potentially causing financial losses, reputation damage, and compliance violations. The attack can be executed from a single attacker or distributed across multiple sources, amplifying its effectiveness.
Mitigation strategies for this vulnerability require immediate implementation of connection timeout configurations and resource management policies within the GoAhead WebServer environment. System administrators should configure appropriate timeout values for both connection establishment and request processing to prevent indefinite connection maintenance. Network-level protections including firewalls and intrusion prevention systems can help detect and block slow HTTP request patterns, while application-level monitoring should track connection counts and resource utilization. The implementation of rate limiting and connection pooling mechanisms can further protect against resource exhaustion attacks. Organizations should also consider upgrading to patched versions of GoAhead WebServer or migrating to more secure web server implementations that properly handle partial HTTP requests and implement robust timeout controls as recommended in industry best practices for web server security.