CVE-2026-85169 in n8n
Summary
by MITRE • 09/03/2026
n8n versions before 1.123.73, 2.35.4, and 2.36.2 contain an expression sandbox escape in the $fromAI handler. $fromAI resolved a caller-supplied placeholder name without requiring it to be an own property and admitted reserved keys; against a primitive input value it returned a live host-prototype reference. An attacker with workflow-build privilege can walk the prototype chain to the Function constructor and compile/execute arbitrary code in the main n8n process, leading to remote code execution.
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Analysis
by VulDB Data Team • 09/03/2026
The vulnerability identified in n8n versions prior to 1.123.73, 2.35.4, and 2.36.2 represents a critical security flaw rooted in improper validation of user-supplied input within the expression sandboxing mechanism. Specifically, the issue resides in the $fromAI handler, which is designed to resolve placeholder names provided by users during workflow execution. The core technical failure lies in the lack of strict property checking when resolving these placeholders. Instead of verifying that the supplied name corresponds exclusively to an own property on the intended object, the implementation allows access to properties inherited through the prototype chain. This oversight permits attackers to supply reserved keys or primitive values that bypass standard sandbox restrictions, effectively breaking out of the isolated execution environment and gaining access to host-level objects such as Function constructors.
From a technical perspective, this flaw enables an attacker with workflow-build privileges to traverse the JavaScript prototype chain up to global object properties. By providing a carefully crafted input value, specifically targeting primitive types that resolve to live references on the Object or Global prototypes, the attacker can retrieve sensitive built-in functions. Once access to the Function constructor is obtained through this sandbox escape, it becomes possible to compile and execute arbitrary code within the context of the main n8n process. This capability transforms what might otherwise be a limited privilege escalation into full remote code execution (RCE), allowing complete compromise of the underlying server infrastructure hosting the automation platform.
The operational impact of this vulnerability is severe due to its potential for unauthorized control over automated workflows and backend systems. An attacker who can create or modify n8n workflows, which requires only basic user privileges in many configurations, can exploit this flaw to execute commands on the host machine. This could lead to data exfiltration, installation of persistent backdoors, lateral movement within internal networks, or disruption of critical business processes managed by the automation platform. The severity is further amplified because n8n is often deployed in environments where it interacts with sensitive APIs and databases, making successful exploitation a significant threat to organizational security posture.
This vulnerability aligns closely with CWE-74 Improper Neutralization Special Elements used in an XML Document known as Injection, specifically in the context of code injection via prototype pollution or sandbox escape mechanisms. It also maps to MITRE ATT&CK technique T1059 Command and Scripting Interpreter, particularly subtechniques involving JavaScript execution, as well as T1203 Exploitation for Client Execution if leveraged through client-side interactions leading to server compromise. The flaw exemplifies the dangers of trusting user input in dynamic scripting environments without rigorous validation against prototype chain traversal attacks.
To mitigate this risk, organizations running n8n must immediately upgrade to version 1.123.73 or later for the v1 branch, or versions 2.35.4 and 2.36.2 and above for the v2 branches. These releases contain patches that enforce strict own-property checks on placeholder resolution within the $fromAI handler, preventing access to reserved keys and prototype chain properties. Additionally, administrators should review workflow permissions to ensure that only trusted users can create or edit workflows containing complex expressions. Implementing web application firewalls with rules targeting known exploitation patterns for sandbox escapes may provide an additional layer of defense during the transition period. Regular security audits focusing on input validation in dynamic expression engines are recommended to prevent similar vulnerabilities from being introduced in future updates.