---
id: CVE-2026-100721
title: >-
  vm2 before 3.12.2 contains an authorization bypass in the NodeVM
  external-module resolver
summary: >-
  vm2 before 3.12.2 contains an authorization bypass in the NodeVM
  external-module resolver. When an embedder configures `require.external` with
  a custom resolver (and `context: 'host'`), `LegacyResolver.customResolve` in
  lib/resolver-comp…
severity: critical
cvss: 9
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H'
cwe:
  - CWE-863
vendor: patriksimek
product: vm2
affected:
  - vm2 < 3.12.2
published: '2026-09-27'
updated: '2026-09-27'
sourceUpdated: '2026-09-27T02:17:18.070'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-100721'
references:
  - url: >-
      https://github.com/patriksimek/vm2/commit/6ac3916da84e060c403e407b6b6318fcc66b0e72
    label: disclosure@vulncheck.com
  - url: >-
      https://github.com/patriksimek/vm2/commit/91034466bfb7f56b95fd48083ec6ca36d058f164
    label: disclosure@vulncheck.com
  - url: >-
      https://github.com/patriksimek/vm2/commit/ab4ee7d803e8c80155e9eb3672226bddbca4aa9c
    label: disclosure@vulncheck.com
  - url: 'https://github.com/patriksimek/vm2/security/advisories/GHSA-5h3f-q97h-ccvc'
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/vm2-before-3.12.2-authorization-bypass-via-custom-resolver
    label: disclosure@vulncheck.com
tags:
  - nvd
  - cve.org
ingestedAt: '2026-09-27T02:41:45.564Z'
---

## Overview

vm2 before 3.12.2 contains an authorization bypass in the NodeVM external-module resolver. When an embedder configures `require.external` with a custom resolver (and `context: 'host'`), `LegacyResolver.customResolve` in lib/resolver-compat.js records the resolved module directory in `this.externals` as `new RegExp('^' + escapeRegExp(resolvedPath))`, without requiring a path separator or end-of-string boundary. Untrusted guest code can therefore require the allowlisted module (e.g. `foo`) and then require the absolute path of a non-allowlisted sibling whose path merely shares the resolved prefix (e.g. `.../node_modules/foo2/index.js`); the sibling passes `isPathAllowedForModule` and is loaded through `hostRequire`, so its top-level code runs in the host process before the exports are wrapped with `vm.readonly`, resulting in a sandbox escape and arbitrary code execution in the host context.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.