CVE-2012-6125 in CHICKEN
Summary
by MITRE
Chicken before 4.8.0 is susceptible to algorithmic complexity attacks related to hash table collisions.
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Analysis
by VulDB Data Team • 11/01/2019
The vulnerability identified as CVE-2012-6125 affects the Chicken Scheme implementation prior to version 4.8.0, exposing it to algorithmic complexity attacks through hash table collision manipulation. This weakness represents a classic denial of service vulnerability that exploits the predictable nature of hash table implementations in interpreted languages. The vulnerability stems from the hash table collision resolution mechanism in Chicken's implementation, where attackers can craft inputs that force hash table operations into worst-case performance scenarios, effectively creating a resource exhaustion attack vector.
Chicken Scheme is an implementation of the Scheme programming language that compiles to C and is widely used in applications requiring scripting capabilities and embedded language processing. The hash table implementation in versions prior to 4.8.0 utilizes a simple chaining approach without proper collision resistance measures. When an attacker provides carefully constructed data that causes hash collisions, the performance degrades from expected O(1) to O(n) operations per hash table access, where n represents the number of collisions. This degradation becomes exponentially worse as more collisions occur, leading to significant performance impact or complete system unresponsiveness.
The operational impact of this vulnerability extends beyond simple performance degradation to encompass complete system availability compromise. Attackers can exploit this weakness by submitting malicious inputs that trigger hash collisions in hash tables used by the interpreter, particularly in scenarios involving large data structures, dictionary operations, or any application code that relies on hash-based data structures. The vulnerability is particularly dangerous in web applications or network services that process untrusted input, as it allows remote attackers to consume system resources and potentially cause service disruption. According to CWE-400, this represents a weakness in algorithmic complexity that can lead to resource exhaustion attacks, while the ATT&CK framework categorizes this under privilege escalation and denial of service techniques.
Mitigation strategies for CVE-2012-6125 focus primarily on upgrading to Chicken Scheme version 4.8.0 or later, which includes improved hash table collision handling and resistance to algorithmic complexity attacks. Additional protective measures include input validation and sanitization to prevent malicious hash collision patterns, implementing resource limits and timeouts for hash table operations, and monitoring for unusual performance patterns that might indicate exploitation attempts. Organizations should also consider implementing rate limiting and input length restrictions for applications processing external data through Chicken Scheme interpreters. The vulnerability highlights the importance of proper hash table implementation in interpreted languages and demonstrates how seemingly minor implementation details can create significant security risks when not properly secured against adversarial inputs.