n8n-MCP Logs Sensitive Request Data on Unauthorized /mcp Requests
Impact
When n8n-mcp runs in HTTP transport mode, incoming requests to the POST /mcp endpoint had their request metadata written to server logs regardless of the authentication outcome. In deployments where logs are collected, forwarded to external systems, or viewable outside the request trust boundary (shared log storage, SIEM pipelines, support/ops access), this can result in disclosure of:
- bearer tokens from the
Authorizationheader - per-tenant API keys from the
x-n8n-keyheader in multi-tenant setups - JSON-RPC request payloads sent to the MCP endpoint
Access control itself was not bypassed — unauthenticated requests were correctly rejected with 401 Unauthorized — but sensitive values from those rejected requests could still be persisted in logs.
Impact category: CWE-532 (Insertion of Sensitive Information into Log File).
Affected
Deployments running n8n-mcp v2.47.10 or earlier in HTTP transport mode (MCP_MODE=http). The stdio transport is not affected.
Patched
v2.47.11 and later.
- npm:
npx n8n-mcp@latest(or pin to>= 2.47.11) - Docker:
docker pull ghcr.io/czlonkowski/n8n-mcp:latest
Workarounds
If users cannot upgrade immediately:
- Restrict network access to the HTTP port (firewall, reverse proxy, or VPN) so only trusted clients can reach the endpoint.
- Switch to stdio transport (
MCP_MODE=stdio, the default for CLI invocation), which has no HTTP surface.
Credit
n8n-MCP thanks @S4nso (Organization / Jormungandr) for reporting this issue.
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| npm package | n8n-mcp | < 2.47.11 | 2.47.11 |
References
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N- Weakness (CWE)
CWE-532- Platform
- npm
- Package
n8n-mcp- Disclosed
- 23.04.2026
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-pfm2-2mhg-8wpx - CC BY 4.0
Vulnerability history: n8n-mcp
All published vulnerabilities of this package (npm package), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 11
- First → latest
- 04.2026 07.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- Critical 1
- High 6
- Medium 4
Disclosures per year
- 2026: 11
-
n8n-MCP Logs Sensitive Request Data on Unauthorized /mcp Requests this entry
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