n8n: Expression Sandbox Escape via Class-Field Sanitizer Rebinding Can Lead to Code Execution

Impact

The expression compiler's sanitizer resolved through a dynamically-scoped this, so a class field named __sanitize rebound it and reached the Function constructor. On the backend, any expression author could run code in the n8n process; in the editor preview, a member's expression could run as JavaScript in the session of whoever opened the workflow. The patch rejects reserved class-member names.

Patches

The issue has been fixed in n8n versions 1.123.76, 2.37.7, and 2.38.2. Users should upgrade to one of these versions or later to remediate the vulnerability.

Workarounds

If upgrading is not immediately possible, administrators should consider the following temporary mitigations:

• Restrict n8n instance access to fully trusted users only.
• Avoid granting workflow-create or workflow-edit permissions to untrusted users.
• Audit existing workflows for unexpected or unfamiliar expressions in node parameters.
• Set N8N_EXPRESSION_ENGINE=vm.

These workarounds do not fully remediate the risk and should only be used as short-term mitigation measures.