CVE-2014-0231 in MacOS X
Summary
by MITRE
The mod_cgid module in the Apache HTTP Server before 2.4.10 does not have a timeout mechanism, which allows remote attackers to cause a denial of service (process hang) via a request to a CGI script that does not read from its stdin file descriptor.
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Analysis
by VulDB Data Team • 09/22/2022
The vulnerability identified as CVE-2014-0231 resides within the mod_cgid module of the Apache HTTP Server version 2.4.9 and earlier, representing a critical security flaw that enables remote attackers to execute denial of service attacks. This issue specifically targets the absence of a timeout mechanism in the CGI daemon module, creating a scenario where malicious actors can exploit the server's handling of CGI scripts to cause persistent process hangs. The vulnerability operates by leveraging the fundamental design flaw in how Apache processes CGI requests that do not properly read from their stdin file descriptor, thereby allowing attackers to maintain connections indefinitely and exhaust server resources.
The technical implementation of this vulnerability stems from the mod_cgid module's failure to implement proper timeout controls during CGI script execution. When a CGI script is invoked through Apache, the server typically establishes a communication channel that includes stdin, stdout, and stderr file descriptors. In affected versions, if a CGI script does not read from stdin, the mod_cgid module continues to maintain the connection in a waiting state indefinitely. This behavior creates a resource exhaustion condition where server processes become tied up in these unresponsive connections, preventing the server from processing legitimate requests. The flaw is particularly insidious because it operates at the core of Apache's CGI handling mechanism, affecting all CGI scripts executed through the mod_cgid module regardless of their specific implementation or security posture.
From an operational impact perspective, this vulnerability creates significant disruption to web server availability and performance. Attackers can maintain persistent connections to the Apache server by submitting CGI requests that never read from stdin, effectively creating a resource starvation condition that consumes available server processes and memory resources. The denial of service effect manifests as gradual server degradation followed by complete unresponsiveness, as the server's process pool becomes exhausted by these hanging connections. Network administrators may observe increased server load, reduced response times, and eventual service outages as the exploitation continues. This vulnerability directly maps to CWE-400, which classifies the issue as an Uncontrolled Resource Consumption vulnerability, and aligns with ATT&CK technique T1499.004 for Network Denial of Service attacks, where adversaries exploit application-level weaknesses to exhaust system resources.
The mitigation strategy for CVE-2014-0231 requires immediate upgrading of Apache HTTP Server to version 2.4.10 or later, where the timeout mechanism has been properly implemented in the mod_cgid module. Organizations should also consider implementing additional protective measures such as setting explicit timeouts for CGI script execution through Apache configuration directives, monitoring server process consumption, and implementing rate limiting for CGI requests. Security teams should conduct comprehensive vulnerability assessments to identify all systems running affected Apache versions and ensure proper patch management procedures are in place. The resolution addresses the root cause by introducing proper timeout controls that automatically terminate CGI script execution after a predetermined period, preventing indefinite resource consumption while maintaining legitimate CGI functionality. This vulnerability highlights the importance of proper resource management in web server configurations and demonstrates how seemingly minor implementation gaps can result in significant security implications.