CVE-2026-27493

n8n is an open source workflow automation platform. Prior to versions 2.10.1, 2.9.3, and 1.123.22, a second-order expression injection vulnerability existed in n8n's Form nodes that could allow an unauthenticated attacker to inject and evaluate arbitrary n8n expressions by submitting crafted form data. When chained with an expression sandbox escape, this could escalate to remote code execution on the n8n host. The vulnerability requires a specific workflow configuration to be exploitable. First, a form node with a field interpolating a value provided by an unauthenticated user, e.g. a form submitted value. Second, the field value must begin with an `=` character, which caused n8n to treat it as an expression and triggered a double-evaluation of the field content. There is no practical reason for a workflow designer to prefix a field with `=` intentionally — the character is not rendered in the output, so the result would not match the designer's expectations. If added accidentally, it would be noticeable and very unlikely to persist. An unauthenticated attacker would need to either know about this specific circumstance on a target instance or discover a matching form by chance. Even when the preconditions are met, the expression injection alone is limited to data accessible within the n8n expression context. Escalation to remote code execution requires chaining with a separate sandbox escape vulnerability. The issue has been fixed in n8n versions 2.10.1, 2.9.3, and 1.123.22. Users should upgrade to one of these versions or later to remediate the vulnerability. If upgrading is not immediately possible, administrators should consider the following temporary mitigations. Review usage of form nodes manually for above mentioned preconditions, disable the Form node by adding `n8n-nodes-base.form` to the `NODES_EXCLUDE` environment variable, and/or disable the Form Trigger node by adding `n8n-nodes-base.formTrigger` to the `NODES_EXCLUDE` environment variable. These workarounds do not fully remediate the risk and should only be used as short-term mitigation measures.

An adversary targets an organization's public-facing n8n Form node used to trigger an AI workflow—e.g., a content ingestion pipeline, customer support automation, or LLM-powered form processor. The attacker submits form data where a field value begins with = followed by an n8n expression: ={{$env.ANTHROPIC_API_KEY}} or ={{$credentials.openAiApi.apiKey}}. If a workflow designer has configured any field to interpolate user-submitted values and that interpolated result is then re-evaluated as an expression, n8n executes the attacker-controlled expression and leaks environment variables or stored credentials in the form response. In an advanced scenario, the attacker chains this with a known n8n sandbox escape to achieve RCE, gaining a foothold on the n8n host and full access to the AI automation infrastructure—including vector databases, LLM API keys, connected enterprise systems, and the ability to modify or inject malicious steps into existing AI workflows.