CVE-2012-4522 in Ruby
Summary
by MITRE
The rb_get_path_check function in file.c in Ruby 1.9.3 before patchlevel 286 and Ruby 2.0.0 before r37163 allows context-dependent attackers to create files in unexpected locations or with unexpected names via a NUL byte in a file path.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 12/20/2021
The vulnerability identified as CVE-2012-4522 represents a critical path traversal flaw in Ruby's file handling mechanisms that emerged in versions prior to specific patch levels. This vulnerability resides within the rb_get_path_check function located in the file.c component of the Ruby interpreter, affecting both Ruby 1.9.3 before patchlevel 286 and Ruby 2.0.0 before revision r37163. The flaw stems from inadequate input validation of file paths, specifically failing to properly handle null byte characters within file path strings.
The technical implementation of this vulnerability exploits a fundamental weakness in Ruby's path validation logic where the presence of a null byte character within a file path string bypasses normal security checks designed to prevent directory traversal attacks. When Ruby processes file operations, the rb_get_path_check function should validate that file paths remain within expected boundaries and do not contain malicious constructs. However, the null byte injection allows attackers to manipulate the path resolution process, effectively truncating the path at the null byte position and enabling arbitrary file creation or modification in unexpected locations. This behavior violates core security principles of input sanitization and path validation that are fundamental to preventing unauthorized file system access.
The operational impact of this vulnerability extends beyond simple file system manipulation to encompass broader security implications for applications built on Ruby. Attackers can leverage this weakness to create files in directories where they would normally lack permissions, potentially leading to privilege escalation scenarios or persistent backdoor creation. The vulnerability enables attackers to bypass security controls designed to prevent directory traversal attacks, which are commonly implemented to restrict file system access to authorized locations. This flaw particularly affects web applications and scripts that process user-supplied file paths, making it exploitable in scenarios involving file upload functionality, configuration file handling, or any application component that accepts external file path inputs.
Mitigation strategies for CVE-2012-4522 focus primarily on immediate patch application to upgrade Ruby installations to versions containing the necessary security fixes. Organizations should prioritize updating their Ruby environments to Ruby 1.9.3 patchlevel 286 or Ruby 2.0.0 revision r37163 and higher, as these versions contain the corrected path validation logic. Additionally, defensive programming practices should be implemented to sanitize all user-supplied file path inputs through proper input validation, ensuring that null byte characters are rejected or properly escaped before processing. The vulnerability aligns with CWE-22 Path Traversal and CWE-77 Path Traversal, representing a classic example of insecure path handling that allows attackers to manipulate file system operations through malformed input. Security controls should also include monitoring for unusual file creation patterns and implementing least privilege access controls to limit the potential damage from successful exploitation attempts. This vulnerability demonstrates the critical importance of proper input validation and the potential for seemingly minor implementation flaws to create significant security risks in system components handling file operations.