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n8n-MCP Logs Sensitive Request Data on Unauthorized /mcp Requests

Moderate severity GitHub Reviewed Published Apr 20, 2026 in czlonkowski/n8n-mcp

Package

Codestin Search App n8n-mcp (npm)

Affected versions

< 2.47.11

Patched versions

2.47.11

Description

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 Authorization header
  • per-tenant API keys from the x-n8n-key header 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.

References

@czlonkowski czlonkowski published to czlonkowski/n8n-mcp Apr 20, 2026
Published to the GitHub Advisory Database Apr 23, 2026
Reviewed Apr 23, 2026

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

EPSS score

Weaknesses

Insertion of Sensitive Information into Log File

The product writes sensitive information to a log file. Learn more on MITRE.

CVE ID

CVE-2026-41495

GHSA ID

GHSA-pfm2-2mhg-8wpx

Source code

Credits

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