CVE-2025-57318 is a Prototype Pollution vulnerability identified in the toCsv function of the csvjson library, affecting versions up to 5.1.0. Prototype Pollution occurs when an attacker is able to manipulate the prototype of a base object, such as Object.prototype in JavaScript, by injecting or modifying properties. This can lead to unexpected behavior in applications using the vulnerable library. In this case, the vulnerability allows an attacker to supply a crafted payload that injects properties into Object.prototype via the toCsv function. The primary consequence reported is denial of service (DoS), which may occur if the polluted prototype causes the application to crash, hang, or behave unpredictably during CSV conversion operations. While the vulnerability does not explicitly mention remote code execution or data leakage, prototype pollution can sometimes be leveraged for more severe attacks depending on the application context. The vulnerability is present in a widely used JavaScript library for converting JSON data to CSV format, which is commonly used in web applications, data processing pipelines, and backend services. No CVSS score or patch links are currently available, and there are no known exploits in the wild at the time of publication. The vulnerability was reserved in August 2025 and published in September 2025, indicating recent discovery and disclosure.

For European organizations, the impact of this vulnerability depends on the extent to which they use the csvjson library in their software stacks. Organizations relying on this library for data transformation, reporting, or integration services could experience denial of service conditions if an attacker supplies malicious input, potentially disrupting business operations or causing application downtime. This could affect sectors with heavy data processing needs such as finance, healthcare, government, and telecommunications. Although the direct impact is DoS, prototype pollution vulnerabilities can sometimes be chained with other vulnerabilities to escalate attacks, so the risk may extend beyond immediate service disruption. Additionally, if the vulnerable library is used in multi-tenant environments or exposed APIs, attackers could exploit this vulnerability remotely, increasing the threat surface. European organizations with strict uptime and availability requirements, such as critical infrastructure providers, may face operational and reputational damage if exploited. Furthermore, compliance with regulations like GDPR mandates prompt vulnerability management, so failure to address this could have legal and financial consequences.

To mitigate this vulnerability, European organizations should first identify all instances of the csvjson library version 5.1.0 or earlier in their codebases and dependencies. Since no official patch is currently available, organizations should consider the following specific actions: 1) Implement input validation and sanitization to reject or neutralize payloads that attempt to manipulate object prototypes before they reach the toCsv function. 2) Use JavaScript security libraries or runtime protections that detect and prevent prototype pollution attacks. 3) Isolate or sandbox components that perform CSV conversion to limit the impact of potential DoS conditions. 4) Monitor application logs and behavior for anomalies indicative of prototype pollution attempts, such as unexpected property injections or crashes during CSV processing. 5) Engage with the maintainers of csvjson to track patch releases and apply updates promptly once available. 6) Consider replacing csvjson with alternative libraries that have been audited and confirmed free of prototype pollution vulnerabilities if immediate patching is not feasible. 7) Conduct security testing, including fuzzing and static analysis, focused on prototype pollution vectors in affected components. These targeted mitigations go beyond generic advice by focusing on the specific nature of prototype pollution and the affected function.