Swagger Vulnerability: Fix Js-yaml Prototype Pollution (CVE-2025-64718)

by Alex Johnson 72 views

This article discusses a medium-severity vulnerability found in swagger-11.2.0.tgz, stemming from a transitive dependency on js-yaml-4.1.0.tgz. The vulnerability, identified as CVE-2025-64718, involves prototype pollution, potentially allowing attackers to modify the prototype of parsed YAML documents. This article provides an in-depth look at the vulnerability, its impact, and how to remediate it.

Understanding the Vulnerability

The Root Cause: js-yaml Prototype Pollution

The core of the problem lies within the js-yaml library, a widely used JavaScript YAML parser and serializer. Versions 4.1.0 and earlier are susceptible to prototype pollution attacks. Prototype pollution occurs when an attacker can manipulate the __proto__ property of an object, leading to modifications in the base object prototype. This can have far-reaching consequences, potentially affecting other parts of the application that rely on the polluted prototype. Specifically, CVE-2025-64718 allows an attacker to modify the prototype of the result of a parsed YAML document. If an application parses untrusted YAML documents, it becomes vulnerable to this type of attack.

The vulnerability arises from the way js-yaml handles certain YAML structures, allowing malicious input to inject properties into the Object.prototype. This injection can overwrite existing properties or introduce new ones, potentially leading to unexpected behavior, security breaches, or denial-of-service conditions. The vulnerability is particularly concerning because YAML is often used for configuration files and data serialization, making it a prime target for attackers seeking to compromise applications.

To fully grasp the impact of this vulnerability, consider a scenario where a web application uses js-yaml to parse configuration files submitted by users. An attacker could craft a malicious YAML file that injects harmful properties into the Object.prototype. These properties could then be inherited by other objects within the application, potentially allowing the attacker to bypass authentication, escalate privileges, or execute arbitrary code. The severity of the impact depends on the specific properties that are injected and how the application utilizes them.

Transitive Dependency: swagger-11.2.0.tgz

In this case, the vulnerable js-yaml-4.1.0.tgz is a transitive dependency of swagger-11.2.0.tgz. A transitive dependency is a dependency that is not directly included in the project but is instead a dependency of one of the project's direct dependencies. This means that even if a project doesn't explicitly use js-yaml, it can still be vulnerable if it uses a library that depends on it. In this specific context, the path to the vulnerable library is /node_modules/js-yaml/package.json, highlighting its location within the project's dependency tree. The swagger-11.2.0.tgz package includes js-yaml as part of its internal workings, making projects that use swagger-11.2.0.tgz indirectly susceptible to the prototype pollution vulnerability.

Understanding the dependency hierarchy is critical for effective vulnerability management. It allows developers to identify the root cause of a vulnerability and take appropriate steps to mitigate it. In this case, the dependency hierarchy is:

  • swagger-11.2.0.tgz (Root Library)
    • :x: js-yaml-4.1.0.tgz (Vulnerable Library)

This shows that js-yaml-4.1.0.tgz is a dependency of swagger-11.2.0.tgz, meaning that upgrading js-yaml or using a patched version of swagger is necessary to address the vulnerability.

Technical Details

CVE-2025-64718: The Identifier

CVE-2025-64718 is the unique identifier assigned to this specific vulnerability. CVE stands for Common Vulnerabilities and Exposures, a standard naming system for security flaws. This identifier provides a consistent way to refer to the vulnerability across different security resources and databases. It allows developers and security professionals to quickly identify and track information about the vulnerability, including its description, impact, and remediation steps.

The vulnerability details associated with CVE-2025-64718 highlight the potential for attackers to exploit the prototype pollution issue in js-yaml. The Common Vulnerability Scoring System (CVSS) score provides a standardized way to assess the severity of the vulnerability. In this case, the CVSS 3 score is 5.3, indicating a medium severity. This score is based on several factors, including the attack vector, attack complexity, privileges required, user interaction, scope, confidentiality impact, integrity impact, and availability impact.

The CVSS score of 5.3 reflects that the vulnerability has a network attack vector, low attack complexity, and requires no privileges or user interaction. The scope is unchanged, meaning that the vulnerability affects the component in which it is found. The confidentiality impact is none, but the integrity impact is low, and the availability impact is none. This means that while the vulnerability does not directly compromise the confidentiality or availability of the system, it can lead to integrity issues, such as the modification of data or the introduction of malicious code.

CVSS v3 Metrics Explained

The CVSS v3 score for CVE-2025-64718 is 5.3 (Medium). Let's break down the metrics:

  • Attack Vector (AV:N): Network. The vulnerability can be exploited over a network.
  • Attack Complexity (AC:L): Low. The attack is relatively easy to execute.
  • Privileges Required (PR:N): None. No privileges are required to exploit the vulnerability.
  • User Interaction (UI:N): None. No user interaction is required to exploit the vulnerability.
  • Scope (S:U): Unchanged. An exploited vulnerability can only affect resources managed by the same security authority.
  • Confidentiality Impact (C:N): None. There is no impact to data confidentiality.
  • Integrity Impact (I:L): Low. There is a potential for some modification of data.
  • Availability Impact (A:N): None. There is no impact to system availability.

For a deeper dive into CVSS v3 scoring, refer to the CVSS v3 Calculator.

Remediation

The recommended solution is to upgrade js-yaml to version 4.1.1 or later. This version contains a patch that addresses the prototype pollution vulnerability. To upgrade, you can use the following command:

npm update js-yaml

However, since js-yaml is a transitive dependency, directly updating js-yaml might not be sufficient. You may need to update swagger-11.2.0.tgz to a version that uses a patched version of js-yaml. Check the release notes or changelog of swagger-11.2.0.tgz to see if a version is available that includes the fix.

If upgrading swagger-11.2.0.tgz is not immediately possible, you can consider using workarounds to mitigate the risk. One approach is to use the --disable-proto=delete flag when running Node.js. This flag disables the __proto__ property, preventing prototype pollution attacks. However, this workaround may have compatibility issues with some applications, so it should be tested thoroughly before being deployed to production.

Another workaround is to use Deno, a modern JavaScript and TypeScript runtime that has built-in protection against prototype pollution. In Deno, pollution protection is enabled by default, making it a more secure environment for running JavaScript code.

Specific Steps to Remediate

  1. Update js-yaml: If your project directly depends on js-yaml, update it to version 4.1.1 or higher.
  2. Update swagger-11.2.0.tgz: Check for newer versions of swagger-11.2.0.tgz that include the updated js-yaml library. Update your project to use the patched version of swagger.
  3. Verify the Fix: After updating, verify that the vulnerability is resolved by re-running your security scans or penetration tests.

Additional Security Measures

Beyond addressing this specific vulnerability, it's important to implement comprehensive security measures to protect your applications from other potential threats. This includes:

  • Regularly updating dependencies: Keep all your project dependencies up to date to ensure that you have the latest security patches.
  • Using a dependency vulnerability scanner: Use a tool like Mend or Snyk to automatically scan your dependencies for known vulnerabilities.
  • Implementing input validation: Validate all user inputs to prevent injection attacks.
  • Following security best practices: Adhere to secure coding practices to minimize the risk of introducing vulnerabilities into your code.

Conclusion

The prototype pollution vulnerability in js-yaml-4.1.0.tgz (CVE-2025-64718) poses a significant risk to applications that parse untrusted YAML documents. By upgrading to js-yaml version 4.1.1 or later, or by using workarounds such as the --disable-proto=delete flag or Deno, you can mitigate this risk and protect your applications from potential attacks. Remember to always keep your dependencies up to date and follow security best practices to maintain a secure development environment.

For more information on web security best practices, visit the OWASP Foundation website.