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Luu, T.J.

GHSA-hw8v-xxg5-vvvx: n8n: Expression Sandbox Escape via Class-Field Sanitizer Rebinding Can Lead to Code Execution

highvulnerability

security

Source: GitHub Advisory DatabaseSeptember 10, 2026CVE-2026-86076

Summary

n8n, a workflow automation tool, had a security flaw where users could escape the expression sandbox (a restricted environment meant to safely run user code) by creating a class field named `__sanitize`, which let them access the Function constructor and run arbitrary code. This meant backend users could execute code in the n8n process, and in the editor preview, someone's expression could run as JavaScript in another person's browser session.

Solution / Mitigation

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. If upgrading is not immediately possible, administrators should 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, and set `N8N_EXPRESSION_ENGINE=vm`. The source notes these workarounds do not fully remediate the risk and should only be used as short-term mitigation measures.