CVE-2012-5372 in Rubinius
Summary
by MITRE
Rubinius computes hash values without properly restricting the ability to trigger hash collisions predictably, which allows context-dependent attackers to cause a denial of service (CPU consumption) via crafted input to an application that maintains a hash table, as demonstrated by a universal multicollision attack against the MurmurHash3 algorithm.
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Analysis
by VulDB Data Team • 03/15/2019
The vulnerability described in CVE-2012-5372 represents a critical weakness in the Rubinius Ruby implementation's hash table implementation that enables predictable hash collision attacks. This flaw specifically targets the MurmurHash3 algorithm used by Rubinius for generating hash values, creating a condition where malicious actors can craft input data that deliberately triggers hash collisions. The vulnerability operates under the Common Weakness Enumeration category of CWE-327, which encompasses weak cryptographic algorithms and hash functions that can be exploited for denial of service attacks. The attack vector leverages the predictable nature of hash collisions to consume excessive CPU resources, effectively rendering applications vulnerable to resource exhaustion attacks that can cripple system performance and availability.
The technical implementation of this vulnerability stems from Rubinius's failure to properly restrict hash value computation during the hash table construction process. When applications using Rubinius maintain hash tables, the underlying MurmurHash3 algorithm becomes susceptible to universal multicollision attacks that allow attackers to generate multiple inputs that hash to the same value. This predictable collision behavior occurs because the hash function does not adequately randomize or obscure the hash generation process, making it possible for attackers to craft specific input sequences that will consistently produce hash collisions. The vulnerability's impact is particularly severe because it operates in a context-dependent manner, meaning that the attack effectiveness varies based on the specific application behavior and hash table usage patterns. This characteristic aligns with the ATT&CK framework's T1499.004 technique for network denial of service, which specifically targets resource exhaustion through algorithmic complexity attacks.
The operational impact of CVE-2012-5372 extends beyond simple resource consumption, as it represents a fundamental flaw in the application's ability to handle hash-based data structures. When exploited, this vulnerability can cause applications to degrade significantly or become completely unresponsive, as hash table operations that should execute in constant time instead degrade to linear or quadratic performance. The attack demonstrates how a seemingly minor implementation detail in hash function design can create catastrophic system-wide effects, particularly when applications rely heavily on hash tables for data management. This vulnerability affects any application running on Rubinius that utilizes hash tables, making it particularly dangerous for web applications, database systems, and any software that processes untrusted input through hash-based data structures. The computational overhead from hash collisions can increase processing time exponentially, leading to complete system paralysis under sustained attack conditions.
Mitigation strategies for CVE-2012-5372 require both immediate patching and architectural considerations for long-term security. The primary solution involves updating to Rubinius versions that properly address hash collision vulnerabilities and implement more robust hash function designs that resist predictable collision attacks. Organizations should also consider implementing hash table size limits and maximum iteration thresholds to prevent resource exhaustion during collision events. Additionally, input validation and sanitization measures can help reduce the impact of crafted inputs that might trigger hash collisions, though these approaches do not address the core vulnerability. Security teams should monitor for applications using vulnerable Rubinius versions and implement runtime protections that detect and limit hash table operations that exceed normal performance thresholds. The vulnerability underscores the importance of proper hash function selection and implementation, as outlined in industry best practices for secure coding and cryptographic implementation standards that emphasize resistance to collision attacks and denial of service scenarios.