n8n Vulnerable to Unauthenticated Denial of Service via MCP Client Registration
Published May 4, 2026 · Updated Oct 23, 2026 · Also known as GHSA-49m9-pgww-9vq6
Original summary
Normalized public record · Updated Oct 23, 2026
n8n Vulnerable to Unauthenticated Denial of Service via MCP Client Registration
Publisher and source text is retained separately from QFinch interpretation.
QFinch assessment
## Impact The MCP OAuth client registration endpoint accepted unauthenticated requests and stored client data without adequate resource controls. An unauthenticated remote attacker could exhaust server memory resources by sending large registration payloads, rendering the n8n instance unavailable. The MCP enable/disable toggle gates MCP access but did not restrict client registrations, meaning the endpoint is reachable regardless of whether MCP access is enabled on the instance.
Evidence: public source recordsAffected products
| Affected package, product or range | Fix status |
|---|---|
| Consult the referenced vendor advisory for affected versions. | Consult source advisory |
Matching a version is only one part of assessing exposure. QFinch has not assessed your environment on this public page.
Remediation
Apply the vendor-supported fixed release or mitigation, then verify the affected component is no longer reachable.
- Confirm the affected product and reachable code path exist in your environment.
- Apply the vendor-supported patch or mitigation from the primary advisory.
- Rescan the exact deployed revision and retain verification evidence.
Evidence coverage
- SSVC priority
- MEDIUM
- Confidence
- 10%
- Aliases
- GHSA-49m9-pgww-9vq6
Scores appear only when corresponding evidence exists. Missing data is never interpreted as zero risk.
Sources and record history
Record history
Published May 4, 2026 · Last refreshed Oct 23, 2026