Race Condition in n8n Git Clone Node Leads to Remote Code Execution

This threat brief details a critical Time-of-Check to Time-of-Use (TOCTOU) race condition affecting n8n, an open-source workflow automation platform, in versions prior to 1.123.64, 2.29.8, and 2.30.1. The vulnerability exists within the Git node's clone operation, which is designed to integrate external code repositories. An authenticated attacker can exploit this race condition by carefully timing a swap between a legitimate directory and a malicious symbolic link (symlink) immediately after n8n performs a path validation check but before the Git clone process completes. This allows the attacker to redirect the cloned repository into n8n's community node directory, effectively planting a crafted, malicious custom node. Upon the next restart of the n8n instance, this malicious custom node is automatically loaded, leading to the execution of arbitrary JavaScript code on the underlying server. This severe vulnerability impacts both self-hosted and cloud deployments of n8n, granting attackers remote code execution capabilities and persistent access to the platform.

Attack Chain

1. An authenticated attacker identifies a vulnerable n8n instance and initiates a Git clone operation via its Git node functionality.
2. The attacker specifies a target directory for the cloned repository within the n8n environment.
3. The n8n application performs an initial path validation check on the specified directory to ensure it is a legitimate and permissible location.
4. Immediately after n8n's path validation and before the actual Git clone operation fully completes, the attacker exploits a TOCTOU race condition by replacing the originally validated directory with a symbolic link (symlink). This symlink is crafted to point to a sensitive location, such as n8n's community node directory (e.g., ~/.n8n/custom/).
5. The Git clone operation proceeds, unaware of the symlink swap, and writes the attacker's specially crafted malicious repository into the community node directory via the symlink. This repository is designed to function as a custom n8n node containing arbitrary JavaScript code.
6. Upon the next restart of the n8n instance (either scheduled or triggered by the attacker), the application automatically discovers and loads the newly planted custom node from the community node directory.
7. The malicious JavaScript code embedded within the custom node is executed on the n8n server with the privileges of the n8n process, resulting in remote code execution (RCE).
8. The attacker achieves persistent control over the n8n instance, enabling further compromise of the system, data exfiltration, or lateral movement within the compromised environment.

Impact

Successful exploitation of this race condition leads to remote code execution (RCE) on the n8n server, allowing an authenticated attacker to execute arbitrary JavaScript code. This can result in complete compromise of the n8n instance, enabling unauthorized access to sensitive data, disruption of critical workflows, or lateral movement within the network. Both self-hosted and cloud environments running vulnerable n8n versions are at risk, making the scope of potential victims broad across various sectors. The attacker gains persistent access as the malicious custom node is loaded automatically upon service restart, posing a significant security threat.

Recommendation

Update n8n to a patched version (1.123.64, 2.29.8, or 2.30.1 or newer) immediately to address the vulnerability. Enable detailed logging for file system changes, particularly within directories associated with n8n custom nodes (e.g., ~/.n8n/custom/) to detect unexpected file or symlink creation. Monitor n8n process execution for any anomalous child processes or network connections that deviate from established baselines, indicating potential arbitrary code execution.