CVE-2025-64718: Fix Js-yaml Prototype Pollution Vulnerability

by Alex Johnson 62 views

This article discusses a medium-severity security vulnerability, CVE-2025-64718, detected in the js-yaml-3.14.0.tgz library. This vulnerability could pose a risk to applications that use this version of the library. We will provide an overview of the vulnerability, its potential impact, and recommended steps for remediation. This detailed analysis aims to help developers and security professionals understand and address this issue effectively.

Vulnerable Library: js-yaml-3.14.0.tgz

The vulnerability resides in js-yaml-3.14.0.tgz, a widely used JavaScript library for parsing and serializing YAML data. YAML (YAML Ain't Markup Language) is a human-readable data serialization format commonly used for configuration files and data exchange between applications. The affected version of the js-yaml library is susceptible to a prototype pollution vulnerability.

  • Library Description: js-yaml is a JavaScript YAML parser and serializer, essential for applications that require processing YAML data.
  • Library Home Page: https://registry.npmjs.org/js-yaml/-/js-yaml-3.14.0.tgz
  • Dependency File Path: /node_modules/js-yaml/package.json
  • Vulnerable Library Path: /node_modules/js-yaml/package.json
  • Dependency Hierarchy:
    • tslint-5.20.1.tgz (Root Library)
      • :x: js-yaml-3.14.0.tgz (Vulnerable Library)
  • Commit Found In: 0c22b39b4f64e2bf88c2b59e4e09bc0b140c91e6
  • Base Branch: develop

Vulnerability Details: Prototype Pollution

The core issue is a prototype pollution vulnerability. Prototype pollution occurs when an attacker can manipulate the __proto__ property of JavaScript objects, allowing them to inject or modify properties on all objects inheriting from that prototype. In the context of js-yaml, this means that by crafting a malicious YAML document, an attacker can potentially modify the prototype of the result of a parsed YAML document.

This vulnerability can have significant security implications. For example, an attacker might be able to inject malicious properties or functions into the base JavaScript object, leading to:

  • Denial of Service (DoS): By modifying critical object properties, the attacker can cause the application to crash or become unresponsive.
  • Remote Code Execution (RCE): In some scenarios, if the application uses the polluted properties in a way that allows code execution, the attacker might be able to execute arbitrary code on the server.
  • Data Tampering: The attacker could modify application data by altering object properties, leading to incorrect or malicious behavior.

The vulnerability is particularly concerning for applications that parse YAML documents from untrusted sources. If an application parses a YAML file uploaded by a user or retrieved from an external API, it could be vulnerable to this attack. To mitigate this risk, it is crucial to update to a patched version of js-yaml and implement additional security measures.

CVSS 3.x Score: 5.3 (Medium)

The Common Vulnerability Scoring System (CVSS) provides a standardized way to assess the severity of security vulnerabilities. The CVSS 3.x score for CVE-2025-64718 is 5.3, which is classified as medium severity. This score reflects the potential impact and exploitability of the vulnerability.

Here's a breakdown of the CVSS 3.x score metrics:

Exploitability Metrics:

  • Attack Vector (AV): Network (N) - The vulnerability can be exploited over a network.
  • Attack Complexity (AC): Low (L) - The vulnerability is relatively easy to exploit.
  • Privileges Required (PR): None (N) - No privileges are required to exploit the vulnerability.
  • User Interaction (UI): None (N) - No user interaction is required to exploit the vulnerability.
  • Scope (S): Unchanged (U) - An exploited vulnerability can only affect resources managed by the same security authority.

Impact Metrics:

  • Confidentiality Impact (C): None (N) - There is no impact to data confidentiality.
  • Integrity Impact (I): Low (L) - There is a potential for a compromise of system integrity.
  • Availability Impact (A): None (N) - There is no impact to system availability.

The medium severity score indicates that while the vulnerability is relatively easy to exploit, the potential impact is limited. However, it is still important to address this vulnerability to prevent potential security breaches and maintain the integrity of your applications.

For more information on CVSS3 Scores, click here.

Suggested Fix: Upgrade to js-yaml 4.1.1

The recommended solution to address CVE-2025-64718 is to upgrade to js-yaml version 4.1.1 or later. This version includes a patch that mitigates the prototype pollution vulnerability. Upgrading the library will help protect your applications from potential attacks and ensure the security of your data.

Upgrade Instructions

To upgrade js-yaml, follow these steps:

  1. Check your package manager: Determine which package manager you are using (e.g., npm, yarn).
  2. Update the dependency: Use the appropriate command to update the js-yaml dependency in your project. For example:
    • npm: npm install js-yaml@4.1.1
    • yarn: yarn upgrade js-yaml@4.1.1
  3. Verify the update: After updating the dependency, verify that the correct version of js-yaml is installed by checking your package.json file or running npm list js-yaml or yarn list js-yaml.
  4. Test your application: Thoroughly test your application to ensure that the update has not introduced any compatibility issues or regressions. Pay particular attention to any code that uses the js-yaml library to parse YAML data.

Additional Security Measures

In addition to upgrading js-yaml, consider implementing the following security measures to further protect your applications:

  • Input Validation: Validate all YAML data that is parsed by your application to ensure that it conforms to the expected schema and does not contain any malicious content.
  • Sandboxing: Run your application in a sandboxed environment to limit the potential impact of any security vulnerabilities.
  • Content Security Policy (CSP): Implement a Content Security Policy (CSP) to prevent the execution of malicious scripts in your application.

Conclusion

CVE-2025-64718 is a medium-severity vulnerability in the js-yaml-3.14.0.tgz library that could potentially lead to prototype pollution attacks. To mitigate this risk, it is crucial to upgrade to js-yaml version 4.1.1 or later and implement additional security measures. By taking these steps, you can help protect your applications from potential security breaches and ensure the integrity of your data. Staying proactive about security vulnerabilities and applying necessary patches and updates is essential for maintaining a secure software environment.

For more information on YAML and its security considerations, visit the YAML official website.