CVE-2026-42282: n8n-MCP Sensitive MCP Tool-call Arguments Logged Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-wg4g-395p-mqv3",
  "modified" : "2026-05-13T13:34:59Z",
  "published" : "2026-04-25T23:35:28Z",
  "aliases" : [ "CVE-2026-42282" ],
  "summary" : "n8n-MCP: Sensitive MCP tool-call arguments logged on authenticated requests in HTTP mode",
  "details" : "### Impact\n\nWhen `n8n-mcp` runs in HTTP transport mode, authenticated MCP `tools/call` requests had their full arguments and JSON-RPC params written to server logs by the request dispatcher and several sibling code paths before any redaction. When a tool call carries credential material — most notably `n8n_manage_credentials.data` — the raw values can be persisted in logs.\n\nIn 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:\n\n- bearer tokens and OAuth credentials sent through `n8n_manage_credentials`\n- per-tenant API keys and webhook auth headers embedded in tool arguments\n- arbitrary secret-bearing payloads passed to any MCP tool\n\nThe issue requires authentication (`AUTH_TOKEN` accepted by the server), so unauthenticated callers cannot trigger it; the runtime exposure is also reduced by an existing console-silencing layer in HTTP mode, but that layer is fragile and the values are still constructed and passed into the logger. The fix removes the leak at the source.\n\nImpact category: **CWE-532** (Insertion of Sensitive Information into Log File). CVSS 3.1 score: **4.3 Medium** (`AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N`).\n\n### Affected\n\nDeployments running n8n-mcp **v2.47.12 or earlier** in HTTP transport mode (`MCP_MODE=http`). The stdio transport short-circuits the relevant log calls and is not affected in practice.\n\n### Patched\n\n**v2.47.13** and later.\n\n- npm: `npx n8n-mcp@latest` (or pin to `>= 2.47.13`)\n- Docker: `docker pull ghcr.io/czlonkowski/n8n-mcp:latest`\n\nThe patch routes tool-call arguments through a metadata-only summarizer (`summarizeToolCallArgs`) that records type, top-level key names, and approximate size — never values. The same pattern was adopted earlier for HTTP request bodies in GHSA-pfm2-2mhg-8wpx.\n\n### Workarounds\n\nIf developers cannot upgrade immediately:\n\n- Restrict access to the HTTP port (firewall, reverse proxy, or VPN) so only trusted clients can authenticate.\n- Restrict access to server logs (no shared SIEM ingestion, no support read-only access) until the upgrade lands.\n- Switch to stdio transport (`MCP_MODE=stdio`, the default for CLI invocation), which has no HTTP surface and short-circuits the affected log calls.\n\n### Credit\n\nn8n-MCP thanks [@Mirr2](https://github.com/Mirr2) (Organization / Jormungandr) for reporting this issue.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "n8n-mcp"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "2.47.13"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/czlonkowski/n8n-mcp/security/advisories/GHSA-wg4g-395p-mqv3"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-42282"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/czlonkowski/n8n-mcp/commit/59b665bda36797823df238aeaf20adb862c9f451"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/czlonkowski/n8n-mcp"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/czlonkowski/n8n-mcp/releases/tag/v2.47.13"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-532" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-25T23:35:28Z",
    "nvd_published_at" : "2026-05-08T20:16:31Z"
  }
}