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Miggo AIRoot Cause AnalysisThe vulnerability exists in the MCP Server Trigger node when it is configured to use n8n OAuth2 authentication. The vulnerability was introduced in n8n version 2.27.0 with the commit e7b1c1c2ef60abb65bf7502c0df5d777276f6ac1, which added the n8n OAuth2 authentication option. The core of the issue is a missing authorization check. While the system authenticates the user by validating the OAuth token, it fails to authorize them by checking if they have the necessary permissions to access the requested workflow. This allows any authenticated user, including a member-level user, to execute any other user's workflow that is protected by n8n OAuth2 by obtaining a valid token for it. The vulnerable functions are McpTrigger.webhook in packages/@n8n/nodes-langchain/nodes/mcp/McpTrigger/McpTrigger.node.ts, which is the entry point for the webhook, and n8nOAuth2Auth in packages/@n8n/nodes-langchain/nodes/mcp/McpTrigger/n8n-oauth2-auth.ts, which performs the incomplete authentication check. The fix for this vulnerability would involve adding an authorization step after the authentication to ensure that the user associated with the OAuth token has the required permissions to access the target workflow.
McpTrigger.webhookpackages/@n8n/nodes-langchain/nodes/mcp/McpTrigger/McpTrigger.node.ts
n8nOAuth2Authpackages/@n8n/nodes-langchain/nodes/mcp/McpTrigger/n8n-oauth2-auth.ts
| Package Name | Ecosystem | Vulnerable Versions | First Patched Version |
|---|---|---|---|
| n8n | npm | >= 2.30.0, < 2.30.1 | 2.30.1 |
| n8n | npm | < 2.29.8 | 2.29.8 |