n8n: Python Code Node AST Validator Bypass

Summary

## Impact An authenticated user with permission to create or modify workflows containing a Python Code node could bypass the AST security validator and access the task executor module namespace. On self-hosted instances where `N8N_BLOCK_RUNNER_ENV_ACCESS=false` is set, this extended to disclosure of environment variables accessible to the task runner process. This issue only affects instances where the Python Task Runner is enabled and `N8N_BLOCK_RUNNER_ENV_ACCESS=true`. ## Patches The issue has been fixed in n8n versions 2.25.7, and 2.26.2. Users should upgrade to one of these versions or later to remediate the vulnerability. ## Workarounds If upgrading is not immediately possible, administrators should consider the following temporary mitigations: - Limit workflow creation and editing permissions to fully trusted users only. - Disable the Python Code node by adding `n8n-nodes-base.code` to the `NODES_EXCLUDE` environment variable, or disable the Python Task Runner entirely. These workarounds do not fully remediate the risk and should only be used as short-term mitigation measures.