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CVE-2026-100723 high CVSS 7.5

Information Disclosure in vm2 (CVE-2026-100723)

Summary

Vulnerability in vm2 (CVE-2026-100723). Confidential information can be exposed externally. Exploitable via zlib. Mitigation: upgrade to 3.12.2 or later.

Original description

The description as published by the source.

Summary

When an application explicitly exposes Node's zlib module through vm2's NodeVM builtin allowlist, an untrusted guest can obtain a pool-backed host Buffer from zlib.deflateSync, create a full-width view of its backing ArrayBuffer, read bytes outside the compressed result, and flip a byte in an unrelated host buffer. The pinned vm2 revision reproduces disclosure and host-memory modification, while a sandbox-local Buffer control remains exact-size and non-mutating.

Technical Details

NodeVM accepts require: { builtin: ['zlib'] }. The builtin resolver reaches addDefaultBuiltin in lib/builtin.js, where the host module is exposed through the generic readonly wrapper. zlib.deflateSync returns a Node Buffer; for a small result, that buffer can use Node's shared pool, whose .buffer is the complete pool rather than only the logical result slice. The guest can therefore call Buffer.from(result.buffer, 0, result.buffer.byteLength) and inspect or modify pooled bytes outside result.

The relevant isolation invariant is that every Buffer crossing into the sandbox owns its complete backing store: byteOffset === 0 and buffer.byteLength === length. vm2's depoolBuffer implementation applies that rule to sandbox-facing Buffer factories, but the generic host-builtin return path does not apply it to the Buffer returned by zlib. The precondition is an embedder that deliberately allowlists zlib; applications that do not expose this builti…

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-2026-100723 has been found in vm2.
Attackers can target a specific entry point like zlib over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 7.5/10.
What to do: upgrade vm2 to 3.12.2 or later.
If unsure, ask your IT team or search "vm2 CVE-2026-100723" on the vendor's site.

CVE-2026-100723 (vm2) — CWE-200 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: zlib / NodeVM / Buffer / zlib.deflateSync
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

Information disclosure (CWE-200) exists in vm2. Attackers reach the vulnerable code path via zlib without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of vm2. Attack surface: zlib / NodeVM / Buffer / zlib.deflateSync.

🔥 Severity

Severity: High (CVSS 7.5/10). Confidential information can be exposed externally.

🔧 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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