n8n: GitHub Trigger 422 Reuse Path Skips Webhook Secret Storage, Causing Signature Verification to Fail-Open

Impact

The GitHub Trigger generated a signing secret when it registered a webhook and verified X-Hub-Signature-256 on each delivery. When GitHub answered the create request with a 422 because a webhook for the URL already existed, the node adopted the remote hook but kept only its id and events, discarding the secret it had generated. Deliveries to that workflow's webhook URL were then accepted from anyone. The patch re-fetches the existing hook by its stored id, re-applies the signing secret, and makes verification fail closed when no secret is stored.

Patches

The issue has been fixed in n8n versions 1.123.76, 2.37.7, and 2.38.2. 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:

• Deactivate and reactivate any GitHub Trigger workflows to force a fresh webhook registration with a new secret, provided the remote GitHub hook has been deleted first so that the 422 reuse path is not taken again.
• Restrict network access to the n8n webhook endpoint to GitHub's published IP ranges only.
• Audit GitHub Trigger workflow static data for entries that contain a webhookId but no webhookSecret, and treat those workflows as unprotected until reactivated successfully.

These workarounds do not fully remediate the risk and should only be used as short-term mitigation measures.