CVE-2007-6750 in macOS Server
Summary
by MITRE
The Apache HTTP Server 1.x and 2.x allows remote attackers to cause a denial of service (daemon outage) via partial HTTP requests, as demonstrated by Slowloris, related to the lack of the mod_reqtimeout module in versions before 2.2.15.
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Analysis
by VulDB Data Team • 11/22/2022
The vulnerability described in CVE-2007-6750 represents a critical denial of service weakness in Apache HTTP Server versions 1.x and 2.x that existed prior to version 2.2.15. This flaw enables remote attackers to systematically disrupt server operations through carefully crafted partial HTTP requests, effectively causing daemon outages that can bring web services offline. The vulnerability specifically stems from the absence of the mod_reqtimeout module, which was designed to address this exact class of attack vectors. The impact of this vulnerability extends beyond simple service disruption as it can be exploited to exhaust server resources and prevent legitimate users from accessing web applications.
The technical mechanism behind this vulnerability involves the exploitation of HTTP request parsing behavior in Apache servers that lack proper timeout configurations for incomplete requests. When attackers send partial HTTP requests that remain incomplete for extended periods, the server maintains these connections in a waiting state indefinitely. This resource exhaustion occurs because Apache's default configuration does not enforce strict timeouts on incomplete requests, allowing malicious actors to open numerous connections that never complete. The Slowloris attack pattern exemplifies this exploitation technique by opening multiple connections and sending partial requests at very slow rates, keeping connections open longer than the server's default timeout settings. This behavior directly maps to CWE-400, which categorizes unchecked resource consumption as a fundamental weakness in software design and implementation.
The operational impact of this vulnerability is severe for organizations relying on Apache HTTP Server for their web infrastructure. Server daemon outages can result in complete service disruption for websites, web applications, and online services, leading to significant business implications including revenue loss, customer dissatisfaction, and potential security reputation damage. The vulnerability particularly affects environments where Apache serves as a primary web server component and where the mod_reqtimeout module has not been properly configured or enabled. Attackers can maintain persistent disruption with minimal resources, as the exploitation requires only a small number of connections to effectively exhaust server capacity. This makes the vulnerability particularly dangerous in production environments where server resources are already constrained and where the impact of service disruption can cascade across dependent systems.
Mitigation strategies for this vulnerability primarily focus on implementing proper timeout configurations and enabling the mod_reqtimeout module. Organizations should upgrade to Apache HTTP Server version 2.2.15 or later where the mod_reqtimeout module is available and properly configured. The module provides granular control over request timeouts including connection timeouts, request header timeouts, and request body timeouts, effectively preventing the resource exhaustion attack patterns. Additionally, administrators should implement proper server configuration practices including setting reasonable timeout values, limiting concurrent connections, and employing connection limiting mechanisms. Network-level protections such as firewalls and intrusion prevention systems can also provide additional layers of defense by monitoring and limiting unusual connection patterns. The vulnerability highlights the importance of following security best practices outlined in the OWASP Top Ten and NIST guidelines for web server hardening, particularly focusing on resource management and input validation controls that prevent exploitation of similar timing-based attack vectors.