CVE-2012-6687 in FastCGI
Summary
by MITRE
FastCGI (aka fcgi and libfcgi) 2.4.0 allows remote attackers to cause a denial of service (segmentation fault and crash) via a large number of connections.
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Analysis
by VulDB Data Team • 06/07/2024
The vulnerability identified as CVE-2012-6687 affects FastCGI implementations, specifically version 2.4.0, creating a significant denial of service condition that can be exploited remotely. FastCGI is a binary protocol for interfacing interactive programs with a web server, designed to reduce the overhead of web server processes by maintaining persistent application processes. This protocol serves as a critical component in web application infrastructure, particularly in environments where high-performance web serving is required. The vulnerability manifests when the FastCGI library encounters an excessive number of concurrent connections, leading to a segmentation fault that ultimately causes the application to crash. This represents a fundamental flaw in connection handling and memory management within the FastCGI implementation.
The technical root cause of this vulnerability lies in the improper handling of connection limits and resource allocation within the FastCGI library. When numerous connections are established simultaneously, the library fails to properly manage memory structures and connection states, resulting in a segmentation fault during the connection processing phase. This flaw operates at the system level where memory corruption occurs due to insufficient bounds checking and inadequate resource management when handling high connection volumes. The vulnerability is classified as a memory corruption issue that can be triggered through network-based attacks, making it particularly dangerous in production environments where web servers may be exposed to untrusted networks. This type of vulnerability aligns with CWE-129, which describes improper validation of array indices, and CWE-787, which covers out-of-bounds write operations, as the memory corruption occurs during connection state management.
The operational impact of this vulnerability extends beyond simple service disruption, as it can be leveraged by attackers to systematically destabilize web applications and services that rely on FastCGI. A successful exploitation can result in complete service unavailability, requiring system administrators to restart affected services and potentially causing cascading failures in dependent systems. Organizations using FastCGI implementations in their web infrastructure face significant risk, particularly those operating high-traffic websites or applications that may be subject to connection flooding attacks. The vulnerability is especially concerning in environments where FastCGI is used with popular web servers such as nginx or Apache, as these platforms may be directly impacted by the segmentation faults. According to ATT&CK framework, this vulnerability maps to T1499.004, which covers network denial of service attacks, and T1566.001, which involves phishing with malicious attachments or links that could be used to initiate the connection flooding attack.
Mitigation strategies for CVE-2012-6687 should focus on both immediate defensive measures and long-term architectural improvements. System administrators should implement connection rate limiting and monitoring to detect unusual connection patterns that may indicate an attack attempt. The most effective immediate solution involves upgrading to a patched version of the FastCGI library, as version 2.4.1 and later contain fixes for the connection handling issues. Network-level protections such as firewall rules and load balancer configurations can help limit the number of concurrent connections to vulnerable services. Additionally, implementing proper resource monitoring and alerting systems can help detect when connection limits are being approached, allowing for proactive intervention before a crash occurs. Organizations should also consider implementing connection pooling and proper timeout configurations to prevent resource exhaustion attacks that could exploit this vulnerability. The remediation process should include thorough testing of patched implementations to ensure that the fix does not introduce new compatibility issues with existing web applications.