CVE-2023-26819 is a vulnerability identified in version 1.7.15 of the cJSON library, a widely used lightweight C library for parsing and printing JSON data. The vulnerability is classified under CWE-440, which pertains to expected behavior violations. Specifically, the issue arises when cJSON processes crafted JSON documents containing extremely large numeric values within arrays, such as {"a": true, "b": [ null,9999999999999999999999999999999999999999999999912345678901234567]}. This malformed input can trigger a denial of service (DoS) condition. The root cause is that the library does not properly handle or validate such large numeric values, leading to unexpected behavior during parsing. This can cause the parser to consume excessive CPU or memory resources, potentially leading to application crashes or unresponsiveness. Since cJSON is often embedded in various software products and systems for JSON processing, this vulnerability could be exploited by an attacker sending malicious JSON payloads to services that utilize the vulnerable cJSON version. The vulnerability does not require authentication or user interaction, as it can be triggered by simply supplying crafted JSON input to the affected system. No known exploits are reported in the wild as of the publication date, and no patches have been linked yet, indicating that remediation may still be pending or in progress.

For European organizations, the impact of this vulnerability primarily concerns service availability and reliability. Systems relying on cJSON 1.7.15 for JSON parsing—such as embedded devices, IoT systems, network appliances, or backend services—may be susceptible to denial of service attacks. An attacker could exploit this by sending specially crafted JSON data, causing the affected application or service to crash or become unresponsive, leading to downtime. This can disrupt business operations, especially in critical infrastructure sectors like telecommunications, manufacturing, or financial services where JSON parsing is common. While the vulnerability does not directly compromise confidentiality or integrity, the availability impact can indirectly affect operational continuity and service-level agreements. Given the absence of known exploits, the immediate risk is moderate; however, the ease of triggering the DoS condition without authentication increases the threat potential. Organizations with automated systems processing external JSON inputs are particularly at risk. Additionally, if the vulnerable cJSON library is embedded in widely deployed software or devices, the attack surface could be broad, amplifying potential disruption.

To mitigate this vulnerability, European organizations should first identify all instances of cJSON 1.7.15 within their software stack, including embedded systems and third-party products. Since no patch is currently linked, organizations should consider the following specific actions: 1) Implement input validation and sanitization at the application or network perimeter to detect and block JSON payloads containing abnormally large numeric values or suspicious structures before they reach the parser. 2) Employ rate limiting and anomaly detection on JSON input endpoints to prevent repeated or high-volume malicious requests that could trigger DoS conditions. 3) Where possible, upgrade or replace the cJSON library with a patched or more robust JSON parsing library that properly handles large numeric values and malformed inputs. 4) For embedded or legacy systems where upgrading is not feasible, consider deploying application-layer firewalls or JSON schema validation tools to enforce strict input constraints. 5) Monitor application logs and system performance metrics for signs of abnormal resource consumption or crashes related to JSON parsing. 6) Engage with vendors of third-party products embedding cJSON to obtain patches or guidance. These targeted mitigations go beyond generic advice by focusing on input validation, detection, and vendor engagement specific to the nature of this vulnerability.