CVE-2021-40663: Prototype Pollution in deep.assign

Background

The deep.assign npm package is a utility library that provides a function for deep merging objects. It is commonly used in JavaScript applications to combine multiple objects into a single object, recursively merging nested properties. The vulnerable version of deep.assign is 0.0.0-alpha.0.

Vulnerability Detail

The deep.assign npm package version 0.0.0-alpha.0 is vulnerable to Prototype Pollution. This vulnerability occurs when user-controllable data is used to modify the prototype of an object, leading to unexpected behavior or security issues. In this case, the package does not properly control modifications to object prototype attributes, allowing an attacker to manipulate the prototype chain and potentially execute arbitrary code or modify existing objects in unintended ways. The severity of this vulnerability is rated as CRITICAL with a CVSS score of 9.8.

Workaround

As a temporary workaround, developers can manually validate and sanitize any user-controllable data before using it to modify object prototypes. This can involve checking the data for unexpected or malicious values and ensuring that only safe and trusted data is used in prototype modifications. Here is an example of how to sanitize user input in JavaScript:

function sanitizeInput(input) {
  // Perform input validation and sanitization
  // Return sanitized input
}

const userControllableData = getUserInput();
const sanitizedData = sanitizeInput(userControllableData);

Object.setPrototypeOf(targetObject, sanitizedData);

This code snippet demonstrates a basic approach to sanitize user input before using it to modify object prototypes.

Conclusion

The deep.assign npm package version 0.0.0-alpha.0 is vulnerable to Prototype Pollution. It is crucial to upgrade to a non-vulnerable version of the package to mitigate the risk of arbitrary code execution or unauthorized modifications to objects. Developers should follow the recommended steps to fix this vulnerability and ensure the security of their applications. For further support on vulnerability remediation, you can reach out to DevNack.com.

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