{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 3.11.3"
      },
      "package": {
        "ecosystem": "npm",
        "name": "vm2"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "3.11.4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [],
  "database_specific": {
    "cwe_ids": [
      "CWE-693"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-29T17:38:33Z",
    "nvd_published_at": null,
    "severity": "LOW"
  },
  "details": "## Summary\n\n`defaultSandboxPrepareStackTrace` in `lib/setup-sandbox.js` (lines 605, 607) appends to a fresh sandbox-realm `lines = []` via `lines[lines.length] = value`. This is the exact invariant-violating pattern that GHSA-9qj6-qjgg-37qq (commit ca195f0, 2026-05-01) just patched in `neutralizeArraySpeciesBatch` and codified as Defense Invariant #11 (\"Bridge-internal containers must not invoke sandbox code\"). A sandbox-installed `Array.prototype[N]` setter fires during the bridge\u0027s safe-default stack-trace formatting and observes / intercepts each appended line.\n\n## Details\n\nThe post-9qj6 audit note in `docs/ATTACKS.md` (line 2111) states:\n\n\u003e Equivalent pattern elsewhere in the bridge: audited; thisFromOtherArguments, otherFromThisArguments, and every other index-write site already use thisReflectDefineProperty or otherReflectDefineProperty. neutralizeArraySpeciesBatch was the lone outlier.\n\nThe audit is scoped to `lib/bridge.js`. `lib/setup-sandbox.js` was not covered. `defaultSandboxPrepareStackTrace` (added under post-#563 hardening for GHSA-v27g) constructs a sandbox-realm `[header]` array and appends each frame via the prototype-walking index assignment:\n\n```\n// lib/setup-sandbox.js, lines 601-610\nconst lines = [header];\nfor (let i = 0; i \u003c callSites.length; i++) {\n    try {\n        lines[lines.length] = \u0027    at \u0027 + callSites[i];\n    } catch (e) {\n        lines[lines.length] = \u0027    at \u003cerror formatting frame\u003e\u0027;\n    }\n}\nreturn lines.join(\u0027\\n\u0027);\n```\n\nThis function runs every time sandbox code reads `error.stack` (or any path that triggers `Error.prepareStackTrace`). At the time it runs, user code has already had the opportunity to install a setter on `Array.prototype[N]`. Because `lines` starts at length 1, the first iteration writes index 1; if `lines[1]` has no own data property, V8 walks the prototype chain and invokes the sandbox-controlled setter.\n\nThe currently-assigned value is the string `\u0027    at \u0027 + callSites[i]` (the wrapped `CallSite` class\u0027s safe `toString()` returns `\u0027CallSite {}\u0027`), which limits the immediate impact to a side channel, not an RCE pivot. The concern is structural rather than exploit-today:\n\n- The just-codified Defense Invariant #11 explicitly requires that any list, set, or map allocated for the bridge\u0027s exclusive use must read and write through identity-stable, prototype-bypassing primitives. This site does not.\n- The `catch` branch at line 607 also uses the same pattern, so a sandbox getter that throws on `callSites[i]` access still routes its retry write through the prototype chain.\n- A future change that makes the appended slot value an object holding a host-realm reference (for example, an enriched frame record) would re-introduce the exact GHSA-9qj6 attack shape against this codepath.\n\nThe fix is mechanical and mirrors the GHSA-9qj6 patch: install entries via `localReflectDefineProperty` so each appended slot is an own data property and the prototype-chain setter is bypassed.\n\n```javascript\n// Suggested patch (sketch)\nlet linesLen = 1;\nfunction append(s) {\n    localReflectDefineProperty(lines, linesLen, {\n        __proto__: null,\n        value: s,\n        writable: true,\n        enumerable: true,\n        configurable: true,\n    });\n    linesLen++;\n}\nfor (let i = 0; i \u003c callSites.length; i++) {\n    try {\n        append(\u0027    at \u0027 + callSites[i]);\n    } catch (e) {\n        append(\u0027    at \u003cerror formatting frame\u003e\u0027);\n    }\n}\n```\n\nThe same pattern at `callSiteGetters[callSiteGetters.length] = {...}` (line 649) runs only at sandbox setup, before user code can install setters, so it is safe today. Converting it for symmetry would be cheap and forward-compatible.\n\n## PoC\n\nvm2 v3.11.2, Node v24.\n\n```javascript\nconst { VM } = require(\u0027vm2\u0027);\nconst result = new VM().run(`\n    var observed = { setterFired: false, capturedValue: null, indexFired: null };\n    Object.defineProperty(Array.prototype, 1, {\n        configurable: true,\n        set(value) {\n            observed.setterFired = true;\n            observed.indexFired = 1;\n            observed.capturedValue =\n                typeof value === \u0027string\u0027 ? value.slice(0, 40) : typeof value;\n        },\n        get() { return undefined; }\n    });\n    var e = new Error(\u0027x\u0027);\n    e.stack;\n    observed;\n`);\nconsole.log(result);\n// {\n//   setterFired: true,\n//   capturedValue: \u0027    at CallSite {}\u0027,\n//   indexFired: 1\n// }\n```\n\nSandbox code observed and intercepted the bridge-internal write to `lines[1]`. Repeating the PoC with the setter installed at multiple indices (0, 1, 2, ...) captures every frame the formatter would otherwise return.\n\n## Impact\n\nHardening / Defense Invariant #11 violation. No direct sandbox escape on the current codebase: the value passed to the setter is a primitive string after the wrapped `CallSite.toString()`, so attacker-controlled code does not gain a host-realm reference from the setter argument alone. The GHSA-9qj6 entry\u0027s \"Considered Attack Surfaces\" note states the audit covered `lib/bridge.js` index-write sites; this filing reports the equivalent pattern in `lib/setup-sandbox.js` so the invariant is uniform across the bridge boundary and future enrichments of the appended record cannot regress into the GHSA-9qj6 shape.",
  "id": "GHSA-q3fm-4wcw-g57x",
  "modified": "2026-05-29T17:38:33Z",
  "published": "2026-05-29T17:38:33Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/patriksimek/vm2/security/advisories/GHSA-q3fm-4wcw-g57x"
    },
    {
      "type": "WEB",
      "url": "https://github.com/patriksimek/vm2/commit/ad31adc1fc4a2c163f2f8c11ab4af206074528fd"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/patriksimek/vm2"
    },
    {
      "type": "WEB",
      "url": "https://github.com/patriksimek/vm2/releases/tag/v3.11.4"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:L/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "vm2 setup-sandbox.js violates Defense Invariant #11 in stack-trace formatter"
}