CVE-2018-1000076 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 Improper Verification of Cryptographic Signature vulnerability in package.rb that can result in a mis-signed gem could be installed, as the tarball would contain multiple gem signatures.. 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-2018-1000076 represents a critical cryptographic signature verification 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 issue resides within the package.rb file and constitutes a weakness categorized under CWE-330 which specifically addresses insufficient entropy in cryptographic systems. The vulnerability stems from an improper verification mechanism that allows malicious actors to exploit the signature validation process by creating mis-signed gems that could be successfully installed on systems.
The technical flaw manifests when RubyGems processes gem packages that contain multiple cryptographic signatures within their tarball archives. The system fails to properly validate that all signatures within the tarball correspond to the same valid source, creating an opportunity for attackers to manipulate the signature verification process. When a gem contains multiple signatures, the flawed verification logic may accept a signature from an untrusted source while ignoring valid signatures from trusted sources, effectively allowing unauthorized modifications to be installed as legitimate packages. This vulnerability directly impacts the integrity and authenticity guarantees that cryptographic signatures are meant to provide in package distribution systems.
The operational impact of this vulnerability extends beyond simple package installation risks as it fundamentally undermines the trust model of RubyGems package management. Attackers could potentially compromise entire Ruby environments by installing malicious gems that appear legitimate due to the flawed signature verification process. The vulnerability creates a persistent threat vector that could be exploited across various Ruby applications and systems that rely on gem packages for dependency management. Organizations using affected Ruby versions face significant risks including potential code execution, data compromise, and supply chain attacks that could affect multiple applications depending on the compromised gems. The vulnerability's exploitation could lead to privilege escalation scenarios and persistent backdoor installations within affected environments.
The fix implemented in RubyGems version 2.7.6 addresses the core verification logic by ensuring that all cryptographic signatures within a gem tarball are properly validated against the same trusted source. This remediation aligns with ATT&CK technique T1195.002 which focuses on supply chain compromise through package managers and addresses the cryptographic weakness identified in the vulnerability. Organizations should immediately upgrade to RubyGems 2.7.6 or later versions to mitigate this risk, while also implementing additional security measures such as verifying gem signatures manually when possible and monitoring for suspicious package installations. The vulnerability demonstrates the critical importance of proper cryptographic verification in package management systems and highlights the need for robust signature validation mechanisms that prevent attackers from exploiting signature ambiguity in software distribution channels.