CVE-2025-62381 is a prototype pollution vulnerability identified in the sveltekit-superforms library, specifically in versions before 2.27.4. The vulnerability resides in the parseFormData function within formData.js, which improperly handles user-supplied form data, allowing an attacker to inject arbitrary string and array properties into the global Object.prototype. Prototype pollution occurs when an attacker manipulates the prototype chain of a base object, causing all objects inheriting from it to be affected. This can result in unexpected behavior such as denial of service due to application crashes, type confusion errors, and in some cases, remote code execution if downstream applications rely on the polluted objects for critical logic or security decisions. The vulnerability has a CVSS 4.0 base score of 8.3, indicating high severity, with attack vector being network-based but requiring high attack complexity and partial attack prerequisites. No authentication or user interaction is required, increasing the risk of exploitation. Although no active exploits have been reported, the potential impact on applications using sveltekit-superforms is significant, especially in web environments where form data is processed extensively. The issue was fixed in version 2.27.4 by correcting the handling of form data to prevent prototype pollution.

For European organizations, the impact of this vulnerability can be substantial, particularly for those developing or maintaining web applications using the sveltekit-superforms library. Exploitation could lead to denial of service, disrupting business operations and causing downtime. Type confusion and prototype pollution can also compromise data integrity, potentially allowing attackers to manipulate application logic or escalate privileges indirectly. In worst-case scenarios, remote code execution could enable attackers to execute arbitrary code on servers or client environments, leading to data breaches or further network compromise. This is especially critical for sectors such as finance, healthcare, and government, where data confidentiality and system availability are paramount. The vulnerability's network-based attack vector means it can be exploited remotely, increasing the threat surface. Given the widespread adoption of JavaScript frameworks in Europe, organizations that have not updated to the patched version remain at risk.

European organizations should immediately upgrade sveltekit-superforms to version 2.27.4 or later to remediate this vulnerability. In addition to patching, developers should audit their codebases for unsafe handling of user input in form processing functions and implement strict input validation and sanitization to prevent prototype pollution. Employing security-focused code reviews and static analysis tools that detect prototype pollution patterns can help identify similar issues. Runtime protections such as Content Security Policy (CSP) and sandboxing of web application components can reduce the impact of potential exploitation. Monitoring application logs for unusual errors or crashes related to object manipulation can provide early indicators of attempted exploitation. Finally, organizations should maintain an inventory of dependencies and apply timely updates to third-party libraries to minimize exposure to known vulnerabilities.