CVE-2017-0903 in RubyGems
Summary
by MITRE
RubyGems versions between 2.0.0 and 2.6.13 are vulnerable to a possible remote code execution vulnerability. YAML deserialization of gem specifications can bypass class white lists. Specially crafted serialized objects can possibly be used to escalate to remote code execution.
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Analysis
by VulDB Data Team • 01/03/2023
The vulnerability identified as CVE-2017-0903 represents a critical remote code execution flaw within RubyGems, a fundamental package management system for ruby applications. This vulnerability affects versions ranging from 2.0.0 through 2.6.13, creating a substantial attack surface across numerous ruby environments and applications that rely on gem management. The flaw stems from insufficient validation during YAML deserialization processes, specifically within the gem specification handling mechanisms that are integral to ruby application deployment and dependency management.
The technical implementation of this vulnerability exploits the YAML deserialization process by bypassing class white lists that should normally restrict which classes can be instantiated during object reconstruction. When ruby gems are installed or processed, the system deserializes YAML formatted gem specifications to understand dependencies and metadata. The vulnerability allows attackers to craft maliciously formatted serialized objects that can bypass these security controls, enabling the instantiation of arbitrary classes during deserialization. This bypass mechanism operates through manipulation of the YAML parsing behavior, specifically targeting the way ruby interprets class references within serialized data structures. The flaw is categorized under CWE-502 as deserialization of untrusted data, which represents a well-known and dangerous attack pattern in software security.
The operational impact of CVE-2017-0903 extends far beyond individual application compromises, as ruby gems are foundational components in web applications, automated deployment systems, and development environments. An attacker who successfully exploits this vulnerability can execute arbitrary code on systems running affected ruby versions, potentially leading to complete system compromise, data exfiltration, or further lateral movement within network environments. The attack vector typically involves manipulating gem specifications during installation or update processes, where the vulnerable deserialization occurs. This vulnerability directly maps to attack techniques described in the MITRE ATT&CK framework under T1059 for command and script injection, as the execution of arbitrary code represents a core component of the attack chain. The widespread adoption of ruby and rubygems in production environments makes this vulnerability particularly dangerous, as exploitation could affect numerous applications across different organizations and industries.
Mitigation strategies for CVE-2017-0903 require immediate remediation through version updates to rubygems 2.6.14 or later, which contain patches addressing the YAML deserialization bypass mechanism. Organizations should implement comprehensive vulnerability scanning to identify systems running affected versions and prioritize patch deployment across all ruby environments. Additional protective measures include implementing strict gem source verification, using gem signing mechanisms, and establishing secure software supply chain practices. Network segmentation and monitoring for unusual gem installation patterns can help detect potential exploitation attempts. The vulnerability highlights the critical importance of secure deserialization practices and demonstrates how seemingly innocuous package management functionality can become a gateway for severe security breaches. Organizations should also consider implementing automated patch management systems to ensure timely updates across their ruby application ecosystems, as this vulnerability represents a classic example of how supply chain attacks can compromise entire software infrastructures through vulnerable dependency management components.