CVE-2025-57353 identifies a prototype pollution vulnerability in the Runtime components of the messageformat package for Node.js, affecting versions before 3.0.2. The vulnerability arises from insufficient validation of nested message keys during message data processing, allowing an attacker to craft input that manipulates the prototype chain of JavaScript objects. By injecting arbitrary properties into Object.prototype, the attacker can influence all subsequent object instances, potentially causing denial of service conditions or unpredictable application behavior. Prototype pollution is a critical security concern because it can alter fundamental object behaviors, leading to security bypasses or application crashes. This vulnerability does not require any privileges or user interaction, making it remotely exploitable over the network. The CVSS score of 5.3 reflects a medium severity, indicating limited confidentiality impact and no direct integrity or availability compromise, but the potential for application instability. No public exploits have been reported yet, but the risk remains significant for applications that rely heavily on the messageformat package for internationalization or message processing. The vulnerability is tracked under CWE-1321, which relates to improper validation of prototype pollution vectors. The lack of patch links suggests that users should monitor official repositories for updates or apply available fixes promptly.

For European organizations, this vulnerability could disrupt Node.js applications that utilize the messageformat package for message formatting or internationalization. Exploitation could lead to denial of service or erratic application behavior, impacting service availability and reliability. While the confidentiality and integrity impacts are limited, the availability and trustworthiness of affected applications may be compromised, potentially affecting customer-facing services or internal tools. Organizations in sectors with high reliance on web applications, such as finance, e-commerce, and public services, could face operational disruptions. Additionally, prototype pollution vulnerabilities can sometimes be chained with other exploits to escalate attacks, increasing risk. The medium CVSS score suggests moderate urgency, but proactive mitigation is essential to prevent exploitation, especially given the ease of remote exploitation without authentication or user interaction.

European organizations should immediately upgrade the messageformat package to version 3.0.2 or later where the vulnerability is fixed. In the absence of an official patch, developers should implement input validation to sanitize and restrict nested message keys, preventing prototype chain manipulation. Conduct thorough code reviews focusing on message data processing and object prototype usage. Employ runtime application self-protection (RASP) or web application firewalls (WAFs) configured to detect and block suspicious payloads targeting prototype pollution. Monitor application logs for anomalies indicative of prototype pollution attempts. Additionally, integrate dependency scanning tools into CI/CD pipelines to detect vulnerable package versions automatically. Educate development teams about prototype pollution risks and secure coding practices related to object manipulation in JavaScript. Finally, maintain an incident response plan to quickly address any exploitation attempts.