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

by Alex Johnson 51 views

This article dives into the details of CVE-2025-64718, a medium-severity vulnerability detected in the js-yaml-3.14.0.tgz library. We will explore the nature of the vulnerability, its potential impact, and the recommended steps to mitigate the risk. This issue was identified by dmyers87 in the frontend discussion category, highlighting the importance of community vigilance in identifying and addressing security concerns. Understanding such vulnerabilities is crucial for maintaining the security and integrity of your applications.

Understanding the Vulnerability

At its core, CVE-2025-64718 exposes a prototype pollution vulnerability within the widely-used js-yaml library. Specifically, versions 4.1.0 and earlier are susceptible to this flaw. Prototype pollution occurs when an attacker can manipulate the __proto__ property of an object during YAML parsing. This manipulation can lead to unexpected behavior, security breaches, and potential compromise of the application. This can occur when parsing untrusted YAML documents, potentially allowing malicious actors to inject arbitrary properties into the base JavaScript object prototype. This could then impact other parts of the application that rely on the expected structure and behavior of JavaScript objects. This vulnerability allows attackers to modify the prototype of the result of a parsed YAML document, affecting all objects inheriting from that prototype.

The js-yaml library, described as a YAML 1.2 parser and serializer, is a fundamental component in many JavaScript projects. Its widespread use makes this vulnerability a significant concern. The library's home page is located at https://registry.npmjs.org/js-yaml/-/js-yaml-3.14.0.tgz. The vulnerability was found in the HEAD commit 7ae889b1abbf39710721c0e586fadd21660e13b0 of the frontend repository and the base branch master.

Deep Dive into the Dependency Hierarchy

To fully grasp the context of this vulnerability, it's essential to understand the dependency chain within the affected project. In this case, the root library, lerna-3.22.1.tgz, depends on info-3.21.0.tgz, which further depends on command-3.21.0.tgz. This then leads to project-3.21.0.tgz, which relies on cosmiconfig-5.2.1.tgz. Finally, cosmiconfig-5.2.1.tgz depends on the vulnerable library, js-yaml-3.14.0.tgz. This chain highlights how deeply embedded the vulnerable library can be within a project, making it critical to address the issue at the root or at the specific dependency level.

The dependency path is as follows:

- lerna-3.22.1.tgz (Root Library)
  - info-3.21.0.tgz
    - command-3.21.0.tgz
      - project-3.21.0.tgz
        - cosmiconfig-5.2.1.tgz
          - js-yaml-3.14.0.tgz (Vulnerable Library)

The path to the dependency file is /package.json, and the path to the vulnerable library is /node_modules/js-yaml/package.json. This information is crucial for identifying the exact location of the vulnerable component within your project.

Impact and Severity

CVE-2025-64718 is classified as a medium-severity vulnerability with a CVSS 3 score of 5.3. While not the highest severity, it still poses a significant risk to applications that parse untrusted YAML documents. The vulnerability allows an attacker to modify the prototype of parsed YAML documents, potentially leading to unexpected behavior or even remote code execution in certain scenarios. The CVSS score reflects the potential impact on integrity, with a low rating, while confidentiality and availability remain unaffected.

The CVSS 3 score is calculated based on the following metrics:

  • Attack Vector: Network
  • Attack Complexity: Low
  • Privileges Required: None
  • User Interaction: None
  • Scope: Unchanged
  • Confidentiality Impact: None
  • Integrity Impact: Low
  • Availability Impact: None

For more detailed information on CVSS3 scores, you can refer to the CVSS Calculator.

Remediation: Upgrading js-yaml

The recommended solution to address CVE-2025-64718 is to upgrade js-yaml to version 4.1.1 or later. This version includes a patch that mitigates the prototype pollution vulnerability. The fix resolution for js-yaml is version 4.1.1, and for the direct dependency lerna, it's version 4.0.0. It is crucial to update the library to protect your applications from potential attacks.

The suggested fix is to upgrade the version. More information about the vulnerability and the fix can be found at https://github.com/nodeca/js-yaml/security/advisories/GHSA-mh29-5h37-fv8m.

Practical Steps for Mitigation

  1. Identify Affected Projects: Use dependency scanning tools or manually inspect your project's package.json files to identify projects that use js-yaml-3.14.0 or earlier.
  2. Update js-yaml: Upgrade the js-yaml dependency to version 4.1.1 or later. You can typically do this using your package manager (e.g., npm install js-yaml@4.1.1 or yarn add js-yaml@4.1.1).
  3. Test Thoroughly: After upgrading, ensure you thoroughly test your application to confirm that the update hasn't introduced any regressions or compatibility issues.
  4. Consider Server-Side Protections: As an additional layer of defense, consider using runtime flags like node --disable-proto=delete (for Node.js) or using Deno, which has prototype pollution protection enabled by default.
  5. Regularly Scan for Vulnerabilities: Integrate vulnerability scanning into your CI/CD pipeline to proactively identify and address security vulnerabilities in your dependencies.

Additional Security Measures

Beyond upgrading js-yaml, consider implementing these additional security measures to further protect your applications:

  • Input Validation: Implement strict input validation to prevent malicious data from being processed by your application.
  • Secure Coding Practices: Follow secure coding practices to minimize the risk of introducing vulnerabilities into your code.
  • Regular Security Audits: Conduct regular security audits to identify and address potential security weaknesses.
  • Web Application Firewall (WAF): Implement a WAF to protect your applications from common web attacks.

Conclusion

CVE-2025-64718 is a medium-severity vulnerability in js-yaml-3.14.0 that exposes applications to prototype pollution attacks. By upgrading to version 4.1.1 or later, you can effectively mitigate this risk. Remember to thoroughly test your application after upgrading and consider implementing additional security measures to further protect your systems.

By staying informed about vulnerabilities like this and taking proactive steps to address them, you can significantly improve the security posture of your applications and protect your users from potential harm. Always keep your dependencies up to date and follow secure coding practices to minimize the risk of introducing vulnerabilities into your code.

For more information on YAML security best practices, visit the OWASP website: OWASP YAML Security Cheat Sheet