CVE-2013-0262 in rack
Summary
by MITRE
rack/file.rb (Rack::File) in Rack 1.5.x before 1.5.2 and 1.4.x before 1.4.5 allows attackers to access arbitrary files outside the intended root directory via a crafted PATH_INFO environment variable, probably a directory traversal vulnerability that is remotely exploitable, aka "symlink path traversals."
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Analysis
by VulDB Data Team • 12/29/2021
The vulnerability identified as CVE-2013-0262 represents a critical directory traversal flaw within the Rack web application framework that affected versions prior to 1.5.2 and 1.4.5. This security issue resides in the rack/file.rb component of Rack's file handling mechanism, specifically within the Rack::File class that manages file serving operations. The vulnerability manifests when applications using Rack process crafted PATH_INFO environment variables, allowing malicious actors to bypass intended directory restrictions and access files outside the designated root directory. The flaw is particularly concerning because it operates through the standard HTTP request processing pipeline, making it easily exploitable through conventional web-based attacks.
The technical implementation of this vulnerability stems from inadequate input validation and path sanitization within Rack's file handling logic. When Rack processes incoming HTTP requests, it relies on the PATH_INFO environment variable to determine which file to serve to the client. In vulnerable versions, the framework failed to properly canonicalize or validate the file paths derived from this variable, allowing attackers to inject directory traversal sequences such as '../' or similar patterns. This weakness enables attackers to navigate beyond the intended document root directory, potentially accessing sensitive system files, configuration data, or other restricted resources that should remain protected from web access. The vulnerability specifically affects Rack's handling of symbolic links, where attackers can exploit symlink traversal to access files in directories that would normally be restricted.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can enable attackers to access critical system resources and potentially compromise entire web applications. Remote exploitation is possible since the vulnerability exists in the request processing layer that handles external input without proper sanitization. Attackers can leverage this flaw to access sensitive data including application configuration files, database connection details, user credentials stored in configuration files, and potentially system-level files that contain administrative privileges or sensitive operational data. The vulnerability affects web applications built on Rack, which includes popular frameworks such as Ruby on Rails, Sinatra, and numerous other web applications that utilize this foundational component for HTTP request handling.
Security professionals should consider this vulnerability in the context of the CWE-22 weakness classification, which specifically addresses directory traversal attacks and improper input handling in file system operations. The vulnerability also aligns with ATT&CK technique T1083, which covers directory and file searches as part of reconnaissance activities. Organizations should prioritize immediate patching of affected Rack versions to mitigate this risk, as the vulnerability has been widely exploited in the wild. Mitigation strategies include updating to Rack versions 1.5.2 or 1.4.5 and later, implementing proper input validation at the application level, and employing web application firewalls to filter suspicious PATH_INFO values. Additionally, security teams should review application configurations to ensure that file serving operations are properly restricted and that symbolic link handling is disabled or properly secured when not required for legitimate application functionality.