# vm2 module allowlist bypass via prefix matching

Source: https://junglewise.ai/threats/duplicate-advisory-external-module-allowlist-uses-a-raw-prefix-test-so-95e7475b  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-17. Updated: 2026-10-01  
License: CC BY 4.0 with a link back

Severity: medium · CVSS 4.2 · Published 2026-09-17

vm2 is a JavaScript virtual machine runtime that uses an allowlist to control which external modules can be loaded. A flaw in the allowlist check uses simple string prefix matching, allowing an attacker to access packages with names that share a prefix with allowlisted packages. An attacker who can run code in NodeVM can reach unauthorized packages and potentially access sensitive data or execute unintended code.

Technologies: [vm2 (npm)](https://junglewise.ai/threats/technologies/vm2), [Patriksimek Vm2](https://junglewise.ai/threats/technologies/patriksimek-vm2). Vendors: [npm](https://junglewise.ai/threats/vendors/npm), [Patriksimek](https://junglewise.ai/threats/vendors/patriksimek).

## Quick answers

**Is This vulnerability exploited in the wild?** No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.

**How severe is This vulnerability?** Medium severity, with a CVSS score of 4.2, published 17 September 2026.

**Which products and versions are affected?** vm2 (npm) <= 3.11.6; Patriksimek Vm2 before 3.11.7.

**Is there a fix for This vulnerability?** A patch was published on 2026-08-24: Fix available in version 3.11.7 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is This vulnerability attacked?** It is attacked over the network.

**Am I affected?** Check whether you run vm2 (npm) or Patriksimek Vm2 at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The isPathAllowedForModule function in lib/resolver-compat.js uses startsWith() for prefix matching instead of boundary-anchored comparison, allowing paths like node_modules/foo2 to match an allowlist entry for node_modules/foo. An attacker can exploit this by performing a relative require from an allowlisted package to reach a prefix-sharing sibling package when transitive loading is disabled. The fix requires path separator validation: checking for path equality or path + separator, not raw prefix matching.

## Affected products

- Patriksimek vm2 before 3.11.7

## Timeline

- 2026-08-24: disclosed: Original advisory GHSA-7q3f-wx44-378m published
- 2026-09-17: advisory: Duplicate advisory GHSA-8mvv-mcc3-xwhh published
- 2026-08-24: patched: Fix available in version 3.11.7

## References

- [https://github.com/patriksimek/vm2/security/advisories/GHSA-7q3f-wx44-378m](https://github.com/patriksimek/vm2/security/advisories/GHSA-7q3f-wx44-378m)

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