CVE-2018-18853 in Spray spray-json
Summary
by MITRE
Lightbend Spray spray-json through 1.3.4 allows remote attackers to cause a denial of service (resource consumption) because of Algorithmic Complexity during the parsing of a field composed of many decimal digits.
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Analysis
by VulDB Data Team • 06/04/2023
CVE-2018-18853 represents a significant algorithmic complexity vulnerability affecting Lightbend Spray spray-json library versions through 1.3.4. This vulnerability falls under the CWE-400 category of Uncontrolled Resource Consumption, specifically manifesting as a resource exhaustion attack that can be exploited remotely. The flaw occurs during the parsing of JSON fields containing an excessive number of decimal digits, creating a scenario where the parser's computational complexity grows exponentially rather than linearly with input size.
The technical implementation of this vulnerability stems from the library's handling of numeric parsing operations within JSON documents. When processing fields with many decimal digits, the spray-json parser exhibits quadratic or worse time complexity behavior, causing the system to consume increasing amounts of CPU cycles and memory resources as the digit count grows. This algorithmic inefficiency allows attackers to craft malicious JSON payloads containing fields with thousands or tens of thousands of decimal digits, which when parsed by vulnerable applications can trigger significant resource consumption.
The operational impact of this vulnerability extends beyond simple denial of service conditions to potentially compromise system availability and stability. In web applications and services that process JSON data from untrusted sources, an attacker can exploit this weakness to exhaust system resources such as CPU time, memory allocation, and thread pools. This can result in service degradation, application crashes, or complete system unavailability, particularly affecting high-traffic applications where multiple concurrent requests could compound the resource exhaustion effects. The vulnerability is particularly concerning in cloud environments where resource consumption directly impacts cost and performance metrics.
Mitigation strategies for CVE-2018-18853 should prioritize immediate library version updates to 1.3.5 or later, which contain the necessary algorithmic complexity fixes. Organizations should implement input validation and size limiting mechanisms for JSON parsing operations, establishing maximum field length constraints to prevent the processing of excessively large numeric values. Network-level protections such as rate limiting and request size restrictions can provide additional defense-in-depth measures. The ATT&CK framework categorizes this vulnerability under T1499.004 for Resource Exhaustion and T1059.007 for Command and Scripting Interpreter, highlighting its potential for both availability and execution-based attacks. Security teams should also consider implementing monitoring and alerting for unusual parsing patterns or resource consumption spikes that may indicate exploitation attempts.