CVE-2017-11343 in scheme
Summary
by MITRE
Due to an incomplete fix for CVE-2012-6125, all versions of CHICKEN Scheme up to and including 4.12.0 are vulnerable to an algorithmic complexity attack. An attacker can provide crafted input which, when inserted into the symbol table, will result in O(n) lookup time.
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Analysis
by VulDB Data Team • 12/13/2022
The vulnerability identified as CVE-2017-11343 represents a critical algorithmic complexity issue within the CHICKEN Scheme implementation that stems from an insufficient resolution of a previously discovered flaw. This weakness specifically affects all versions of CHICKEN Scheme through version 4.12.0, creating a persistent security risk that has remained unaddressed despite prior awareness of the underlying problem. The vulnerability manifests through the symbol table implementation which fails to properly handle certain input patterns that can cause the lookup operations to degrade from their expected constant time complexity to linear time complexity.
The technical flaw resides in the symbol table data structure implementation where crafted input can trigger collision patterns that cause the internal hash table or linked list structures to degenerate into worst-case performance scenarios. When an attacker supplies maliciously constructed input that maps to the same hash bucket or creates long collision chains, the symbol lookup operations transition from O(1) to O(n) performance characteristics. This degradation occurs because the implementation does not adequately implement collision resolution mechanisms or does not properly handle hash table resizing and rehashing operations under adversarial input conditions.
The operational impact of this vulnerability extends beyond simple performance degradation to create a potential denial of service condition that can be exploited by malicious actors. Attackers can construct specific inputs that cause the Scheme interpreter to spend excessive computational resources during symbol resolution operations, effectively creating a resource exhaustion attack that can consume system memory and processing power. The vulnerability is particularly dangerous in environments where CHICKEN Scheme processes untrusted input, such as web applications or sandboxed execution environments, as it allows attackers to craft inputs that will cause the system to become unresponsive or crash entirely.
This vulnerability aligns with CWE-400 which categorizes algorithmic complexity issues as a fundamental weakness in software design that can lead to denial of service conditions. The attack pattern closely follows techniques described in the ATT&CK framework under the T1499.004 subtechnique for "Resource Exhaustion" where adversaries consume system resources through algorithmic complexity attacks. The incomplete fix for CVE-2012-6125 indicates a pattern of inadequate vulnerability remediation where the original solution was not comprehensive enough to prevent all variants of the underlying algorithmic complexity problem.
Mitigation strategies for CVE-2017-11343 require immediate upgrades to CHICKEN Scheme versions that properly address the symbol table implementation issues. Organizations should implement input validation and sanitization measures to prevent malicious inputs from reaching the symbol table processing components. The recommended approach includes deploying patched versions of CHICKEN Scheme that utilize proper hash table implementations with collision resolution, dynamic resizing capabilities, and consistent performance characteristics regardless of input patterns. Additionally, monitoring systems should be configured to detect unusual processing patterns that may indicate exploitation attempts, and rate limiting mechanisms should be implemented to prevent excessive symbol table operations from overwhelming system resources.