CVE-2018-1107 in is-my-json-valid
Summary
by MITRE • 03/30/2021
It was discovered that the is-my-json-valid JavaScript library used an inefficient regular expression to validate JSON fields defined to have email format. A specially crafted JSON file could cause it to consume an excessive amount of CPU time when validated.
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Analysis
by VulDB Data Team • 04/06/2021
The vulnerability identified as CVE-2018-1107 resides within the is-my-json-valid JavaScript library, a widely used tool for validating JSON data structures against defined schemas. This library implements validation rules for various data types including email addresses, which are typically validated using regular expressions. The flaw manifests when the library employs an inefficient regular expression pattern to validate email format fields, creating a potential denial of service condition that can be exploited through carefully crafted JSON input.
The technical implementation of this vulnerability stems from the use of a regular expression that exhibits exponential time complexity during pattern matching operations. When processing JSON data containing maliciously constructed email fields, the validation algorithm enters into a computationally expensive state where the time required to complete validation grows exponentially with input size. This behavior creates a classic denial of service scenario where an attacker can craft JSON payloads that cause the validating application to consume excessive CPU resources, potentially leading to system resource exhaustion and application unresponsiveness.
The operational impact of this vulnerability extends beyond simple performance degradation, as it represents a significant security risk in environments where JSON validation is performed on untrusted input. Attackers can exploit this weakness by submitting maliciously formatted JSON documents that trigger the inefficient regular expression, causing validation processes to consume disproportionate computational resources. This vulnerability affects applications that rely on the is-my-json-valid library for input validation, potentially impacting web services, API endpoints, and backend systems that process JSON data from external sources.
This vulnerability aligns with CWE-400, which describes improper restriction of excessive CPU consumption, and demonstrates the importance of proper input validation practices in preventing denial of service attacks. The ATT&CK framework categorizes this as a resource exhaustion technique under the T1496 sub-technique, where adversaries leverage inefficient algorithms to consume system resources. Organizations utilizing this library face potential risks including service disruption, increased operational costs due to resource consumption, and potential exploitation for broader attack vectors that could leverage the resulting system instability.
Mitigation strategies for CVE-2018-1107 require immediate updates to the is-my-json-valid library to versions that address the inefficient regular expression implementation. System administrators should also implement input validation rate limiting and monitoring to detect anomalous validation behavior that may indicate exploitation attempts. Additionally, organizations should consider alternative validation libraries that have been audited for performance characteristics and do not exhibit similar regular expression complexity issues. Regular security assessments of third-party dependencies and implementation of automated dependency monitoring can help prevent similar vulnerabilities from affecting systems in the future.