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CVE-2026-43999 critical CVSS 9.9

Authorization Flaw in vm2 (CVE-2026-43999)

Summary

Vulnerability in vm2 (CVE-2026-43999). Successful exploitation can lead to full system takeover. Exploitable via builtin. Mitigation: upgrade to 3.11.0 or later.

Original description

The description as published by the source.

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 child_process 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; ['*', '-child_process'] 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 — SPECIAL_MODULES (line 61) — does NOT include module…

Source: NIST National Vulnerability Database NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-43999 has been found in vm2.
Attackers can target a specific entry point like builtin over the network to misuse the product.
Successful exploitation can lead to full system takeover. CVSS score: 9.9/10.
What to do: upgrade vm2 to 3.11.0 or later.
If unsure, ask your IT team or search "vm2 CVE-2026-43999" on the vendor's site.

CVE-2026-43999 (vm2) — CWE-863 / CVSS v3 9.9
Attack vector: remote (network-reachable) / no user interaction
Attack surface: builtin / module / child_process / SPECIAL_MODULES
Patched: 3.11.0 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

Incorrect authorization (CWE-863) exists in vm2. Attackers reach the vulnerable code path via builtin.

📍 Affected scope

Check the vendor advisory for the affected versions of vm2. Attack surface: builtin / module / child_process / SPECIAL_MODULES.

🔥 Severity

Severity: Critical (CVSS 9.9/10). Successful exploitation can lead to full system takeover.

🔧 How to fix

Update to 3.11.0.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'vm2' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    grep -r 'vm2' . | grep -v node_modules

    リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で vm2 を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Apply patch patch 
    Upgrade vm2 to 3.11.0

    ステージング環境で 3.11.0 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。

  3. 3
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

npm vm2
[{"type":"SEMVER","events":[{"introduced":"3.10.5"},{"fixed":"3.11.0"}]}]

References

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