In n8n versions prior to 2.25.7 and 2.26.2, an authenticated user with permission to create or modify workflows can introduce prototype mutations into the sandbox context used by the Merge node's SQL Query mode. Because this sandbox context is cached and reused across all workflow executions on the instance, these mutations persist and affect subsequent executions by other users or projects. This leads to exposure of workflow data processed by other users on the same instance. The vulnerability is specific to multi-user instances where more than one user can create and execute workflows containing the Merge node in SQL Query mode. The issue is resolved in n8n versions 2.25.7 and 2.26.2.

A low-privileged authenticated user on a multi-user n8n instance can exploit this vulnerability to intercept workflow data belonging to other users by polluting the shared sandbox context used by the Merge node's SQL Query mode. This results in unauthorized data exposure between sessions. The vulnerability does not affect single-user instances or users without workflow creation and execution permissions involving the Merge node in SQL Query mode.

This vulnerability is fixed in n8n versions 2.25.7 and 2.26.2. Users should upgrade to at least one of these versions to remediate the issue. Since the product is not a cloud service, remediation requires applying the official fixes by upgrading the affected software. Patch status is confirmed by the vendor advisory information embedded in the description.