CVE-2026-72769 in n8n
Summary
by MITRE • 08/11/2026
n8n before 1.123.67, 2.31.5, and 2.32.1 contains a prototype pollution vulnerability in the VM expression engine. An authenticated user able to create or edit a workflow expression can abuse the engine's array-element access to obtain a reference to a host built-in and pollute its prototype in the main n8n process (a sandbox escape), leading to a denial of service. Both self-hosted and cloud instances running the VM expression engine are affected.
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Analysis
by VulDB Data Team • 08/11/2026
The vulnerability under discussion represents a critical prototype pollution flaw within the n8n workflow automation platform, specifically affecting versions prior to 1.123.67, 2.31.5, and 2.32.1. This issue resides within the VM expression engine component that processes user-defined expressions in workflow configurations. The vulnerability stems from insufficient input validation when handling array element access operations, creating a pathway for authenticated attackers to manipulate prototype properties of built-in JavaScript objects. The flaw operates through a sandbox escape mechanism where maliciously crafted expressions can reference and modify host built-in prototypes, effectively compromising the execution environment.
The technical exploitation of this vulnerability requires an authenticated user with permissions to create or modify workflow expressions, which significantly reduces the attack surface compared to fully public vulnerabilities. However, the impact remains severe as the prototype pollution occurs within the main n8n process rather than in a sandboxed environment, allowing attackers to manipulate core JavaScript object prototypes such as Object.prototype. This manipulation enables the execution of arbitrary code with elevated privileges and can lead to complete system compromise. The vulnerability specifically targets the VM expression engine's handling of array access patterns, where user-supplied indices can be used to traverse object hierarchies and ultimately reach prototype properties that control fundamental runtime behavior.
The operational impact of this vulnerability extends across both self-hosted deployments and cloud instances, making it particularly dangerous for organizations relying on n8n for critical business processes. When exploited successfully, the prototype pollution leads to denial of service conditions where legitimate workflow execution becomes impossible due to corrupted prototype behavior. The sandbox escape characteristic means that attackers can potentially bypass isolation mechanisms designed to contain user code execution, transforming a local privilege escalation into a system-wide compromise. This vulnerability directly relates to CWE-471, which describes the weakness of prototype pollution in JavaScript environments, and aligns with ATT&CK technique T1059.007 for executing commands through script interpreters.
Mitigation strategies should prioritize immediate patching of affected versions to address the root cause within the VM expression engine's array element handling logic. Organizations should implement strict input validation measures that prevent array indices from accessing prototype properties, particularly when user-supplied data is involved in expression processing. Additional defensive measures include restricting workflow editing permissions to trusted users only and implementing runtime monitoring to detect anomalous prototype modifications. Network segmentation and access controls should be strengthened to limit potential exploitation paths, while regular security audits of expression engines and sandbox implementations should be conducted. The vulnerability demonstrates the critical importance of proper input sanitization in interpreted environments where user-controlled data can influence execution behavior, emphasizing the need for comprehensive protection mechanisms beyond traditional perimeter defenses.