Security Digest · Vulnerability record
CVE-2026-43999: vm2 has a NodeVM builtin allowlist bypass via `module` builtin's `Module._load` that allows sandbox escape
vm2 is an open source vm/sandbox for Node.js.
CVSS 9.9 Critical EPSS 1.0% · p61
Should you act?
Critical, preconditions apply
Severe if exploited, but exploitation needs conditions that may not apply to you. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.
- Not in CISA KEV, but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
- EPSS 1.0%, percentile 61: FIRST’s model estimates a 1.0% chance of exploitation activity in the next 30 days, higher than 61% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
- Needs an account (low (any account)). Exposure depends on who can log in.
- Only applies if your dependency tree includes
vm2(npm) = 3.10.5, fixed in 3.11.0. Check your lockfile, including transitive dependencies.
What it is
vm2 is an open source vm/sandbox for Node.js. Prior to 3.11.0, NodeVM's builtin allowlist can be bypassed when the module builtin is allowed (including via the '' wildcard). The module builtin exposes Node's Module.load(), which loads any module by name directly in the host context, completely bypassing vm2's builtin restriction. This allows sandboxed code to load excluded builtins like childprocess and achieve remote code execution. This vulnerability is fixed in 3.11.0.
From the GitHub advisory
Summary NodeVM's builtin allowlist can be bypassed when the module builtin is allowed (including via the '' wildcard). The module builtin exposes Node's Module.load(), which loads any module by name directly in the host context, completely bypassing vm2's builtin restriction. This allows sandboxed code to load excluded builtins like childprocess and achieve remote code execution.
Severity Critical (CVSS 3.1: 9.9)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
- Attack Vector: Network — sandboxed code is typically received from external sources (user-submitted scripts, plugin code) - Attack Complexity: Low — no special conditions required; ['', '-childprocess'] is a common, documented pattern - Privileges Required: Low — attacker needs only the ability to submit code to the sandbox, which is the intended use case - User Interaction: None - Scope: Changed — escape from sandbox boundary to host system - Confidentiality Impact: High — arbitrary command execution on the host - Integrity Impact: High — arbitrary command execution on the host - Availability Impact: High — arbitrary command execution on the host
Affected Component - lib/builtin.js — makeBuiltinsFromLegacyOptions() (lines 109-117) — includes module in '' expansion - lib/builtin.js — addDefaultBuiltin() (lines 86-90) — loads module with generic readonly wrapper - lib/builtin.js — SPECIALMODULES (line 61) — does NOT include module
Weakness type: CWE-863, CWE-829.
Product: vm2 (npm) · Assigned by: GitHub_M · Published: 2026-05-13
Affected and fixed versions
| Ecosystem | Package | Vulnerable | First fixed |
|---|---|---|---|
| npm | vm2 | = 3.10.5 | 3.11.0 |
| Vendor | Product | Affected versions (per CVE record) |
|---|---|---|
| patriksimek | vm2 | < 3.11.0 |
Severity scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_M | 3.1 | 9.9 Critical | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H |
| redhat-SADP | 3.1 | 9.9 Critical | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H |
| GitHub | 3.1 | 9.9 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H |
- Attack vector: network (remotely reachable)
- Attack complexity: low
- Privileges required: low (any account)
- User interaction: none
- Scope: changed (can affect other components)
CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.
Exploitation and urgency
- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation poc, automatable no, technical impact total.
- FIRST EPSS (model of 2026-10-21): 0.97% probability of exploitation activity in the next 30 days; percentile 61.
Timeline
- — GitHub-reviewed advisory GHSA-947f-4v7f-x2v8 published (critical)
- — CVE record published by GitHub_M
- — CVE record last updated
Sources and references
Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.
Vendor and project advisories, patches
- access.redhat.com access.redhat.com
Vulnerability records
- GitHub Advisory GHSA-947f-4v7f-x2v8 github.com
- CVE.org record CVE-2026-43999 cve.org
- NVD entry CVE-2026-43999 nvd.nist.gov
Other references from the CVE record and advisory
- github.com github.com
- access.redhat.com access.redhat.com
- RHBZ#2477196 bugzilla.redhat.com
- security.access.redhat.com security.access.redhat.com