CVE-2017-14033 in macOS
Summary
by MITRE
The decode method in the OpenSSL::ASN1 module in Ruby before 2.2.8, 2.3.x before 2.3.5, and 2.4.x through 2.4.1 allows attackers to cause a denial of service (interpreter crash) via a crafted string.
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Analysis
by VulDB Data Team • 05/10/2026
The vulnerability identified as CVE-2017-14033 represents a critical denial of service flaw within the OpenSSL::ASN1 module of Ruby implementations. This issue affects multiple versions of the Ruby programming language including versions prior to 2.2.8, 2.3.x versions before 2.3.5, and 2.4.x versions through 2.4.1. The vulnerability stems from insufficient input validation within the decode method, which processes ASN1 encoded data structures commonly used in cryptographic operations and certificate handling. When attackers provide maliciously crafted strings to this decode method, the Ruby interpreter experiences unexpected behavior leading to interpreter crashes and complete service disruption.
The technical nature of this vulnerability falls under CWE-129, which addresses improper validation of array indices, and more specifically relates to improper input validation within cryptographic libraries. The flaw occurs during the parsing of ASN1 structures where the decode method fails to properly validate the length fields and structural boundaries of the encoded data. This inadequate validation allows attackers to craft input sequences that cause buffer overflows or invalid memory access patterns within the Ruby interpreter's memory management system. The vulnerability is particularly dangerous because it operates at the interpreter level rather than application level, meaning a single malformed ASN1 input can bring down the entire Ruby process regardless of the application's own error handling mechanisms.
From an operational perspective, this vulnerability presents significant risk to systems running Ruby applications that process external ASN1 data such as SSL/TLS certificates, PKCS#7 signed messages, or any cryptographic data that relies on OpenSSL::ASN1 for parsing. Attackers can exploit this flaw by sending specially crafted ASN1 encoded payloads to any Ruby service that processes such data, potentially causing widespread service disruption across web applications, API endpoints, and backend services. The impact extends beyond simple denial of service as the interpreter crash can lead to cascading failures in application stacks that depend on Ruby processes, particularly in containerized environments where process restarts may not be immediate or predictable.
Security practitioners should prioritize immediate patching of affected Ruby versions to prevent exploitation, with recommended remediation including upgrading to Ruby 2.2.8, 2.3.5, or 2.4.2 respectively. Additional mitigations include implementing input validation layers at application boundaries, rate limiting for ASN1 processing endpoints, and network segmentation to limit exposure of vulnerable services. Organizations should also consider implementing intrusion detection systems that can identify patterns of ASN1 data manipulation attempts. The vulnerability aligns with ATT&CK technique T1499.004, which covers network denial of service, and represents a classic example of how cryptographic library flaws can be leveraged for service disruption attacks. Monitoring for interpreter crashes and implementing proper error handling for cryptographic operations can help detect exploitation attempts and provide early warning of potential attacks against Ruby applications processing external data.