CVE-2018-1000079 in Ruby
Summary
by MITRE
RubyGems version Ruby 2.2 series: 2.2.9 and earlier, Ruby 2.3 series: 2.3.6 and earlier, Ruby 2.4 series: 2.4.3 and earlier, Ruby 2.5 series: 2.5.0 and earlier, prior to trunk revision 62422 contains a Directory Traversal vulnerability in gem installation that can result in the gem could write to arbitrary filesystem locations during installation. This attack appear to be exploitable via the victim must install a malicious gem. This vulnerability appears to have been fixed in 2.7.6.
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Analysis
by VulDB Data Team • 02/21/2023
The vulnerability identified as CVE-2018-1000079 represents a critical directory traversal flaw in the RubyGems package management system affecting multiple Ruby versions including 2.2.9 and earlier, 2.3.6 and earlier, 2.4.3 and earlier, and 2.5.0 and earlier. This weakness resides in the gem installation process where the system fails to properly validate file paths during package extraction, allowing malicious actors to manipulate the installation behavior. The vulnerability operates under the Common Weakness Enumeration framework as CWE-22, which specifically addresses improper limitation of a pathname to a restricted directory, commonly known as path traversal or directory traversal attacks. The attack vector requires social engineering or privilege escalation where a victim must willingly install a malicious gem package, making this a supply chain security risk that leverages user trust in the package management ecosystem.
The technical implementation of this vulnerability stems from insufficient input validation within the gem installation routines where relative path references are not properly sanitized before being used to determine target filesystem locations. When a gem package is installed, the system processes the gem's internal structure and extracts files to the target directory without adequate checks on path components such as parent directory references or absolute path indicators. This allows an attacker to craft a malicious gem that, when installed, writes files to arbitrary locations on the filesystem rather than confined to the intended gem directory. The exploitation mechanism aligns with ATT&CK technique T1195.002 which describes supply chain attacks through package managers, where adversaries compromise package repositories or create malicious packages to achieve unauthorized code execution or privilege escalation. The vulnerability essentially permits attackers to bypass normal filesystem access controls and potentially overwrite critical system files or inject malicious code into the target environment.
The operational impact of this vulnerability extends beyond simple file system manipulation and can lead to privilege escalation, system compromise, and persistent backdoor installation. An attacker who successfully exploits this vulnerability can place malicious executables, configuration files, or other payloads in system directories such as /usr/bin, /etc, or other locations where the ruby process has write permissions. This capability enables attackers to establish persistence, escalate privileges, or create covert communication channels. The vulnerability is particularly dangerous in environments where users have the ability to install gems or where automated systems automatically install packages from untrusted sources. Organizations using Ruby applications in production environments are at risk of having their systems compromised through this attack vector, especially when gem repositories are not properly vetted or when automated deployment systems lack proper package integrity verification. The fix implemented in Ruby 2.7.6 demonstrates the severity of the issue and the need for proper input sanitization during package installation processes.
The remediation strategy involves immediate upgrading to Ruby 2.7.6 or later versions where the vulnerability has been patched through enhanced path validation and sanitization routines. System administrators should implement strict gem repository policies, including certificate validation, package signature verification, and automated scanning of gem contents for malicious patterns. Organizations should also consider implementing network segmentation to prevent unauthorized gem installations and establish clear procedures for gem dependency management. The vulnerability highlights the importance of secure software supply chain practices and proper input validation at all levels of the application stack. Security teams should monitor for malicious gems in public repositories and implement continuous integration security testing that validates package integrity before deployment. This case study exemplifies the critical need for robust input validation in package managers and demonstrates how seemingly minor flaws in file system operations can result in significant security implications across the entire system architecture.