Description
Zigbee2MQTT's ExternalJSExtension.getFilePath() (lib/extension/externalJS.ts) joins a `name` parameter received via an MQTT message (topic zigbee2mqtt/bridge/request/extension/save) into the extensions base path using path.join(basePath, name) with no sanitization. Because path.join() resolves `../` sequences, a name such as `../../tmp/evil.js` escapes the intended extensions directory. The extension handler only validates that the name ends in .js/.mjs/.cjs, writes the file, and then dynamically imports it via Node.js import(), achieving remote code execution. Requires the `enable_external_js` config option (off by default, but commonly enabled in legacy installs) and MQTT broker access, which is frequently unauthenticated in real deployments. The identical unsanitized getFilePath() is also used by the extension-removal handler, enabling arbitrary file deletion.
Published: 2026-08-05
Score: 8.1 High
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
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Remediation

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History

Wed, 05 Aug 2026 13:15:00 +0000

Type Values Removed Values Added
Description Zigbee2MQTT's ExternalJSExtension.getFilePath() (lib/extension/externalJS.ts) joins a `name` parameter received via an MQTT message (topic zigbee2mqtt/bridge/request/extension/save) into the extensions base path using path.join(basePath, name) with no sanitization. Because path.join() resolves `../` sequences, a name such as `../../tmp/evil.js` escapes the intended extensions directory. The extension handler only validates that the name ends in .js/.mjs/.cjs, writes the file, and then dynamically imports it via Node.js import(), achieving remote code execution. Requires the `enable_external_js` config option (off by default, but commonly enabled in legacy installs) and MQTT broker access, which is frequently unauthenticated in real deployments. The identical unsanitized getFilePath() is also used by the extension-removal handler, enabling arbitrary file deletion.
Title Zigbee2MQTT External JS Extension Path Traversal Leading to Remote Code Execution
Weaknesses CWE-22
References
Metrics cvssV3_1

{'score': 8.1, 'vector': 'CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'}

Subscriptions

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cve-icon MITRE

Status: PUBLISHED

Assigner: TuranSec

Published:

Updated: 2026-08-05T12:26:25.594Z

Reserved: 2026-08-05T12:23:34.967Z

Link: CVE-2026-71279

cve-icon Vulnrichment

No data.

cve-icon NVD

No data.

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-08-05T15:30:17Z

Weaknesses