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CVE-2026-100721 critical CVSS 9.0

Authorization Flaw in vm2 (CVE-2026-100721)

Summary

Vulnerability in vm2 (CVE-2026-100721). Successful exploitation can lead to full system takeover. Exploitable via NodeVM. Mitigation: upgrade to 3.12.2 or later.

Original description

The description as published by the source.

Summary

At source revision 91034466bfb7f56b95fd48083ec6ca36d058f164 of vm2 3.11.8, an untrusted NodeVM guest can turn one allowlisted custom-resolved module into authorization for a separate file whose path merely shares the resolved path's string prefix. LegacyResolver.customResolve stores the resolved path in this.externals as ^ without an end or separator boundary; a later absolute require of a sibling such as foo2/index.js therefore passes the external check and is loaded through hostRequire when the configured context is host. The decisive attack loaded foo as FOO_OK and then executed the prefix-sharing sibling, which returned PREFIX_PWN after invoking child_process; an otherwise identical control denied the sibling with ENOTFOUND.

Technical Details

The affected configuration is a documented NodeVM use in which the embedder sets require.external to {modules: ['foo'], transitive: false}, supplies a custom resolver that returns the foo directory, sets a root directory, and uses context: 'host'. The guest controls the require specifiers and requests the allowlisted bare name before requesting the absolute path of the prefix-sharing sibling. The test entry point is deliberately outside the configured root so ordinary node_modules lookup misses and the custom resolver is consulted.

The source-to-sink path is:

  • NodeVM.run executes guest code and creates the module-specific require function at lib/nodevm.js:516-575.
  • `D…

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-2026-100721 has been found in vm2.
Attackers can target a specific entry point like NodeVM over the network to misuse the product.
Successful exploitation can lead to full system takeover. CVSS score: 9.0/10.
What to do: upgrade vm2 to 3.12.2 or later.
If unsure, ask your IT team or search "vm2 CVE-2026-100721" on the vendor's site.

CVE-2026-100721 (vm2) — CWE-863 / CVSS v3 9.0
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: NodeVM / LegacyResolver.customResolve / this.externals / hostRequire
Patched: 3.12.2 — 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 NodeVM without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of vm2. Attack surface: NodeVM / LegacyResolver.customResolve / this.externals / hostRequire.

🔥 Severity

Severity: Critical (CVSS 9.0/10). Successful exploitation can lead to full system takeover.

🔧 How to fix

Update to 3.12.2.

🛡️ 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 3.12.2

    ステージング環境で 3.12.2 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":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.12.2"}]}]

References

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