CVE-2017-0902 in RubyGems
Summary
by MITRE
RubyGems version 2.6.12 and earlier is vulnerable to a DNS hijacking vulnerability that allows a MITM attacker to force the RubyGems client to download and install gems from a server that the attacker controls.
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Analysis
by VulDB Data Team • 05/10/2026
The vulnerability identified as CVE-2017-0902 represents a critical security flaw in RubyGems client implementations prior to version 2.6.12, specifically targeting the gem installation and dependency resolution process. This vulnerability stems from insufficient validation of DNS responses during the gem fetching operation, creating a window of opportunity for man-in-the-middle attackers to manipulate the gem resolution process. The flaw allows adversaries to intercept DNS queries and redirect requests to malicious servers, effectively compromising the integrity of the gem installation process.
The technical implementation of this vulnerability resides in the RubyGems client's handling of DNS resolution for gem sources and dependencies. When a user attempts to install a gem, the client performs DNS lookups to resolve gem repository addresses. In affected versions, the client does not properly validate the DNS responses or implement secure DNS resolution mechanisms, making it susceptible to cache poisoning or DNS spoofing attacks. This weakness aligns with CWE-358, which addresses improper input validation in security-critical contexts, and specifically targets the DNS resolution process where trust assumptions are improperly placed.
The operational impact of this vulnerability extends beyond simple code execution or data theft, as it fundamentally compromises the trust model of the Ruby package ecosystem. An attacker who successfully exploits this vulnerability can install malicious gems that contain backdoors, credential stealers, or other malicious payloads that execute with the privileges of the user running the gem installation command. The attack vector typically involves network interception in public Wi-Fi networks, compromised DNS servers, or attacks on network infrastructure that allows DNS response manipulation. This vulnerability affects the entire Ruby development ecosystem, as developers rely on RubyGems for package management and dependency resolution.
The exploitation of this vulnerability follows patterns consistent with ATT&CK technique T1059.007 for Ruby and T1566 for malicious content delivery through compromised package repositories. Organizations and developers using affected RubyGems versions face significant risk of supply chain attacks where legitimate-looking gems are replaced with malicious alternatives. The vulnerability is particularly dangerous in enterprise environments where developers may not be aware of the compromised package sources, and automated deployment systems may silently install malicious code. Security teams should note that this vulnerability does not require special privileges to exploit, making it accessible to attackers with basic network access.
Mitigation strategies for CVE-2017-0902 focus primarily on upgrading to RubyGems version 2.6.13 or later, which implements proper DNS validation and secure resolution mechanisms. Additionally, organizations should implement network-level security measures including DNSSEC validation, network segmentation, and monitoring for anomalous DNS traffic patterns. Developers should consider using gem signing verification and maintaining strict control over their gem sources. The vulnerability demonstrates the critical importance of secure package management in modern development environments, where supply chain attacks can compromise entire application ecosystems. Organizations should also implement regular security audits of their RubyGem dependencies and establish secure development practices that include dependency verification and source authentication.