GHSA-cw9w-vv67-hf73: Npm/n8n vulnerability
Impact
The OAuth token endpoint bound an authorization code's first access token to the consented resource, but not its refresh token. Refreshing only checked that the requested resource was registered, not that it matched the original grant. An OAuth client approved for one workflow could refresh with a different workflow's URL and get a valid, unapproved token for it. The patch binds refresh tokens to the granted resource and rejects mismatches.
Exploitation requires the attacker to register an OAuth client, convince an authenticated user to approve that client for one known protected resource, and know the URL of a second protected resource that the consenting user is permitted to execute.
Patches
The issue has been fixed in n8n versions 2.38.1 and 2.37.7. Users should upgrade to this version or later to remediate the vulnerability.
Workarounds
If upgrading is not immediately possible, administrators should consider the following temporary mitigations: - Restrict n8n instance access to fully trusted users only. - Deactivate MCP Trigger, form, and webhook workflows that are protected by the n8n OAuth server if they are not required. - Audit connected OAuth clients and revoke any that are not recognized or no longer needed. - Require re-authorization for all existing OAuth clients after upgrading, as previously issued refresh tokens did not store the original resource binding.
These workarounds do not fully remediate the risk and should only be used as short-term mitigation measures.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
npm/n8nto a version that resolves this vulnerability.Fixed in 2.37.7 - Upgrade
Upgrade
npm/n8nto a version that resolves this vulnerability.Fixed in 2.38.1 - Upgrade
Upgrade
n8nto a version that resolves this vulnerability.Fixed in 2.38.1 - Upgrade
Upgrade
n8nto a version that resolves this vulnerability.Fixed in 2.37.7 - Configuration
Deactivate MCP Trigger, form, and webhook workflows that are protected by the n8n OAuth server if they are not required.
n8n MCP Trigger, form, and webhook workflows protected by the n8n OAuth server = deactivated - Compensating control
Restrict n8n instance access to fully trusted users only.
- Operational
After upgrading, require re-authorization for all existing OAuth clients (previously issued refresh tokens did not store the original resource binding).
- Operational
Audit connected OAuth clients and revoke any that are not recognized or no longer needed.
Event History
Frequently Asked Questions
What conditions are required to exploit this issue?
An attacker must register an OAuth client, persuade an authenticated user to approve it for a known protected resource, and know the URL of a different protected resource that the same user is authorized to execute. The attacker can then use a refresh operation to obtain a token for that unapproved resource.
Which workflows are most relevant to exposure?
The affected resources are MCP Trigger, form, and webhook workflows protected by the n8n OAuth server. Exposure depends on users consenting to an attacker-controlled OAuth client and having permission to execute another protected workflow.
What should administrators do if they cannot upgrade immediately?
Restrict access to the n8n instance to fully trusted users. Deactivate OAuth-server-protected MCP Trigger, form, and webhook workflows that are not required, and audit connected OAuth clients.
Which versions contain the fix?
The issue is fixed in n8n 2.38.1 and 2.37.7. Upgrade to one of these versions or a later version.