How to Fix CVE-2023-29017- A Critical Sandbox Escape Vulnerability in vm2 Sandbox Library


On April 6th, 2023, KAIST WSP Lab researchers reported the Remote Code Execution Flaw in vm2, CVE-2023-29017. The vulnerability is rated 9.8 on the CVSS scoring system. This Sandbox Escape Vulnerability in vm2 could allow an attacker to escape the sandbox and access the underlying host system fully.

This flaw is particularly concerning because VM2 is often used in production environments to provide security-critical services. Any attacker that can exploit this flaw would gain full access to the systems on which these applications are running. This could lead to data loss, service interruption, or complete system compromise.

Fortunately, the team that maintains VM2 has already released a patch for this flaw. This article will explain how to Fix CVE-2023-29017 and mitigate the risk of exploitation.

vm2 Sandbox Library- A Brief Introduction 

vm2 is a JavaScript sandbox library that provides an isolated environment for running untrusted code on Node.js. 

vm2 is designed to create a secure sandbox around untrusted code that can be run safely without affecting the host machine. It is widely used in the Node.js community, with nearly four million weekly downloads, and is used in 721 packages

It is especially useful for developers who need to run untrusted code in a controlled environment, such as when developing plugins or extensions for web applications.

Features of vm2 Sandbox Library

Following are some features of vm2 Sandbox Library: 

  • Secure execution of untrusted code: vm2 Sandbox Library enables the execution of untrusted code in a secure environment. It does this by running the untrusted code separately from the host process.
  • Controlled console output: The sandbox provides full control over its console output. This allows developers to control what information is displayed to users and helps to prevent information leaks.
  • Limited access to process methods: The sandbox has limited access to the host process’s methods. This helps to ensure that the untrusted code cannot access or modify sensitive information.
  • Module support: The sandbox allows using built-in and external modules from within the sandbox. This provides flexibility for developers who need to use specific modules in their code.
  • Access control: The library allows developers to limit access to certain or all built-in modules. This helps prevent untrusted code from accessing modules it should not have access to.
  • Secure exchange of data and callbacks: The sandbox allows for the secure exchange between sandboxes. This helps to prevent unauthorized access to sensitive information.
  • Immunity to known attacks: The library is designed to be immune to all known attack methods, ensuring that the untrusted code cannot be used to compromise the security of the host process.
  • Transpiler support: The library supports transpilers, allowing developers to use modern JavaScript features with the sandbox.
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How Does it Work? 

Using the internal VM module, the vm2 Sandbox Library creates a secure context for untrusted code. This ensures the code cannot access or modify sensitive information in the host process. The library also uses Proxies to intercept and customize operations on objects, preventing untrusted code from escaping the sandbox and accessing sensitive information. 

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Additionally, the library overrides the built-in require function to control access to modules, further enhancing the security of the sandbox by preventing untrusted code from accessing modules it should not have access.

Summary of CVE-2023-29017

CVE-2023-29017 is a Sandbox Escape Vulnerability in vm2 that could allow attackers to bypass its sandbox protections and execute arbitrary shellcode on the host machine. 

Associated CVE IDCVE-2023-29017
DescriptionA Critical Sandbox Escape Vulnerability in vm2 Sandbox Library
Associated ZDI ID
CVSS Score10.0 Critical
VectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Impact Score6.0
Exploitability Score3.9
Attack Vector (AV)Network
Attack Complexity (AC)Low
Privilege Required (PR)None
User Interaction (UI)None
ScopeChanged
Confidentiality (C)High
Integrity (I)High
availability (a)High

This flaw was released right after six months when another bug was resolved for vm2 that could have been weaponized for arbitrary operations on the underlying machine. The researchers have also released a proof-of-concept exploit demonstrating how the flaw can be exploited.

The flaw specifically exists in the “clone()” method used by vm2. This method creates a copy of an object but fails to properly copy the “__proto__” property. This leaves the new object open to manipulation, which can then be used to break out of the sandbox.

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vm2 Sandbox Library Versions Affected by CVE-2023-29017

CVE-2023-29017, the critical sandbox escape vulnerability in the vm2 sandbox library, affects all library versions before version 3.9.15. If you are using an older version of the vm2 library, it is recommended that you update to the latest version to protect against exploitation. As the vulnerability has been fixed in version 3.9.15 of the library, you’re protected if you’re using that version or a later version.

How to Fix CVE-2023-29017-  A Critical Remote Code Execution Flaw in vm2 Sandbox Library?

There are two primary ways to mitigate this vulnerability:

Patch the vm2 library

Patching the vm2 library is the recommended approach for mitigating the CVE-2023-29017 vulnerability. This involves upgrading to version 3.9.15 or a later version, including a vulnerability fix. This will help you protect your system against vulnerability exploitation. 

Use a different sandboxing solution

If you cannot patch the vm2 library or prefer a different sandboxing solution, you can explore other options without the same flaw. This approach can be useful if you have other reasons to switch sandboxes or cannot upgrade to a patched version of vm2.

Some alternative sandboxing solutions include:

  1. Node VM: A built-in sandboxing solution that provides a secure environment for executing untrusted code.  
  2. Worker Threads: You can run untrusted code in separate threads to prevent it from affecting the main thread.

The CVE-2023-29017 critical Remote Code Execution Flaw in the vm2 sandbox library is a significant security concern for developers. Immediate action must be taken to mitigate this vulnerability and improve system security–learn how to Fix CVE-2023-29017.  

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Upgrading to the latest version of vm2 sandbox library is necessary and updating code to use the latest version of the library is crucial to prevent the flaw. It is essential to follow secure coding practices, such as input validation and sanitization, and regularly review and update software to avoid similar vulnerabilities in the future. Taking these steps can enhance system security and protect against potential threats. 

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