CVE-2014-7818 in Ruby on Rails
Summary
by MITRE
Directory traversal vulnerability in actionpack/lib/action_dispatch/middleware/static.rb in Action Pack in Ruby on Rails 3.x before 3.2.20, 4.0.x before 4.0.11, 4.1.x before 4.1.7, and 4.2.x before 4.2.0.beta3, when serve_static_assets is enabled, allows remote attackers to determine the existence of files outside the application root via a /..%2F sequence.
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Analysis
by VulDB Data Team • 04/03/2022
The vulnerability described in CVE-2014-7818 represents a critical directory traversal flaw within the Ruby on Rails framework's static file serving mechanism. This issue affects multiple versions of the Action Pack component, specifically targeting Rails 3.x versions prior to 3.2.20, 4.0.x versions prior to 4.0.11, 4.1.x versions prior to 4.1.7, and 4.2.x versions prior to 4.2.0.beta3. The vulnerability manifests when the serve_static_assets configuration parameter is enabled, creating a pathway for malicious actors to exploit the application's file handling capabilities. The attack vector utilizes a specific sequence involving the /..%2F pattern, which when processed by the static middleware, allows unauthorized access to files outside the designated application root directory. This flaw operates at the core of web application security by exploiting improper input validation in file path resolution mechanisms, potentially exposing sensitive system files, configuration data, or other restricted resources that should remain isolated from user access.
The technical implementation of this vulnerability stems from inadequate sanitization of user-supplied input within the static file serving middleware of Ruby on Rails. When a request containing the /..%2F sequence is processed, the application fails to properly normalize or validate the file path before attempting to serve the requested resource. This allows attackers to manipulate the path resolution logic to traverse directories beyond the intended application boundaries. The flaw specifically resides in the action_dispatch/middleware/static.rb file within the Action Pack library, where the middleware handles static asset requests. The vulnerability is classified as a directory traversal or path traversal attack, which is commonly categorized under CWE-22 in the Common Weakness Enumeration system. The attack leverages the fact that the application's path resolution logic does not adequately handle encoded sequences or malformed path references that could be used to escape the application's root directory context.
The operational impact of CVE-2014-7818 extends beyond simple information disclosure, as it provides attackers with the ability to determine the existence of arbitrary files on the server's filesystem. This reconnaissance capability allows malicious actors to map the underlying system structure and identify potentially sensitive files that might contain credentials, configuration details, or other confidential information. The vulnerability enables attackers to perform a form of passive reconnaissance that can reveal the presence of backup files, log files, or other system artifacts that could be exploited in subsequent attack phases. From an attacker's perspective, this vulnerability can be used as a reconnaissance tool to gather intelligence about the target system, potentially leading to more severe exploits. The impact is particularly concerning in environments where Rails applications are deployed with static asset serving enabled, as this configuration is common in production deployments and often includes sensitive application files that should remain protected from unauthorized access.
Mitigation strategies for this vulnerability require immediate patching of affected Rails versions to their respective secure releases. Organizations should upgrade to Rails 3.2.20, 4.0.11, 4.1.7, or 4.2.0.beta3 respectively, depending on their current version. Additionally, administrators should review their application configurations to ensure that serve_static_assets is not enabled in production environments unless absolutely necessary. The implementation of proper input validation and path normalization should be enforced at all levels of the application stack, with specific attention to how file paths are processed in middleware components. Security monitoring should include detection of unusual file access patterns that might indicate directory traversal attempts, and organizations should consider implementing web application firewalls or intrusion detection systems that can identify and block such attacks. The vulnerability aligns with ATT&CK technique T1083 (File and Directory Discovery) and demonstrates the importance of proper input validation and least privilege access controls in preventing unauthorized system access. Organizations should also conduct comprehensive security assessments to identify other potential path traversal vulnerabilities in their application code and dependencies, as this type of flaw can manifest in various forms throughout complex web applications.