CVE-2018-17850 in JsonCpp
Summary
by MITRE
An issue was discovered in JsonCpp 1.8.4. An unhandled exception vulnerability exists in Json::Value::clear() in json_value.cpp after throwing an instance of "Json::LogicError what(): requires complex value." Specially crafted JSON requests can cause an unhandled exception resulting in denial of service. An attacker can send malicious JSON to trigger this vulnerability.
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Analysis
by VulDB Data Team • 05/19/2023
The vulnerability identified as CVE-2018-17850 represents a critical denial of service weakness within the JsonCpp library version 1.8.4. This flaw manifests in the Json::Value::clear() method located in the json_value.cpp file, where the library fails to properly handle exceptional conditions during JSON parsing operations. The vulnerability specifically occurs when the library attempts to process malformed or specially crafted JSON input that triggers a Json::LogicError exception with the message "requires complex value." This unhandled exception cascade causes the application to terminate unexpectedly, creating a denial of service condition that can be reliably exploited by malicious actors.
The technical implementation of this vulnerability stems from inadequate error handling mechanisms within the JsonCpp library's value management system. When the clear() method encounters JSON data that does not conform to expected complex value structures, it throws a LogicError exception without proper exception handling or recovery mechanisms. This behavior aligns with CWE-401, which addresses improper handling of exceptional conditions in software applications. The flaw demonstrates a classic example of exception safety issues where the library does not maintain consistent state or provide graceful degradation when encountering malformed input data.
From an operational perspective, this vulnerability presents significant risks to applications that rely on JsonCpp for JSON processing and parsing. Attackers can exploit this weakness by sending carefully constructed JSON payloads that trigger the LogicError condition during the clear() operation, causing applications to crash or become unresponsive. The impact extends beyond simple application termination as it can affect entire service availability, particularly in high-traffic environments where JSON processing is frequent. This vulnerability particularly affects web applications, APIs, and services that process user-provided JSON data without proper validation or sanitization, making it a prime target for denial of service attacks.
The exploitation of CVE-2018-17850 follows established patterns found in the ATT&CK framework under the T1499 category for network denial of service attacks. This vulnerability can be leveraged in various attack scenarios including distributed denial of service campaigns, where attackers send multiple malicious JSON requests to overwhelm target systems. Organizations should implement immediate mitigations including upgrading to JsonCpp versions that address this specific vulnerability, implementing input validation and sanitization layers, and deploying application firewalls or web application firewalls that can detect and block suspicious JSON patterns. Additionally, developers should incorporate proper exception handling mechanisms and consider using alternative JSON libraries that have demonstrated better error resilience and handling capabilities. The vulnerability highlights the importance of robust input validation and exception handling in security-critical libraries, as it demonstrates how seemingly minor error handling gaps can create significant operational risks and potential attack vectors.