CVE-2016-1000104 in mod_fcgid
Summary
by MITRE
A security Bypass vulnerability exists in mod_fcgid through 2016-07-07 in the FcgidPassHeader Proxy.
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Analysis
by VulDB Data Team • 10/25/2024
The security bypass vulnerability identified as CVE-2016-1000104 affects the mod_fcgid module, a critical component in Apache web server configurations that handles FastCGI processes. This vulnerability specifically resides within the FcgidPassHeader Proxy functionality, which is designed to pass HTTP headers from the proxy server to the FastCGI application. The flaw represents a significant weakness in the module's header handling mechanism that could allow unauthorized access to sensitive information or bypass security controls that should normally be enforced by the web server configuration. The vulnerability was discovered and documented in the context of the mod_fcgid module's version control system, with the specific patch date of 2016-07-07 indicating the timeline for remediation efforts.
The technical implementation of this vulnerability stems from inadequate validation and sanitization of HTTP headers within the FcgidPassHeader Proxy functionality. When mod_fcgid processes requests through the proxy mechanism, it fails to properly validate or filter incoming header data, creating an avenue for malicious actors to manipulate header values that should be restricted or controlled. This weakness can be exploited to bypass authentication mechanisms, access restricted resources, or manipulate the behavior of FastCGI applications that depend on proper header handling. The vulnerability manifests when the module processes headers that are intended to be filtered or blocked by security policies, allowing them to pass through to the backend FastCGI application unfiltered. This represents a classic case of insufficient input validation and access control enforcement, which aligns with CWE-284 Access Control flaws and CWE-20 Improper Input Validation.
The operational impact of CVE-2016-1000104 extends beyond simple information disclosure, as it can enable attackers to circumvent critical security controls within Apache web server deployments that utilize mod_fcgid. Organizations running vulnerable configurations may experience unauthorized access to protected content, potential data breaches, and compromised application integrity. The vulnerability's exploitation can lead to privilege escalation scenarios where attackers gain access to resources that should be restricted to authenticated users or specific system components. In environments where mod_fcgid is used for hosting sensitive applications such as content management systems, web applications, or enterprise services, this bypass could result in significant security incidents. The vulnerability affects any deployment where FastCGI applications are proxied through Apache with mod_fcgid enabled, making it particularly concerning for large-scale web infrastructure that relies on this module for application processing.
Mitigation strategies for this vulnerability primarily involve applying the official patch released by the mod_fcgid development team on 2016-07-07, which addresses the specific header validation issue within the FcgidPassHeader Proxy. Organizations should also implement additional security measures such as restricting the use of FcgidPassHeader directive where possible, configuring proper access controls, and monitoring for anomalous header patterns in web server logs. Network-level defenses including web application firewalls and intrusion detection systems can provide additional layers of protection by monitoring for suspicious header manipulation patterns. Security teams should also conduct comprehensive vulnerability assessments to identify all systems running affected versions of mod_fcgid and ensure that all Apache installations are updated to versions that contain the necessary security fixes. The vulnerability's classification under ATT&CK tactic TA0001 Initial Access and technique T1078 Valid Accounts demonstrates its potential for enabling unauthorized system access through compromised header handling mechanisms. Organizations should also consider implementing principle of least privilege configurations and regularly reviewing their web server security configurations to prevent similar vulnerabilities from emerging in other components of their infrastructure.