BREW-n8n-mcp-CVE-2026-55608 — n8n-MCP: Incorrect authorization can expose default-scope workflow version backups in multi-tenant HTTP mode

Affected: Homebrew: n8n-mcp

## Summary

In multi-tenant HTTP mode (`ENABLE_MULTI_TENANT=true`), an authenticated tenant could, under certain conditions, reach n8n-mcp's local default-scope `workflow_versions` backups instead of being confined to its own tenant scope. This affects n8n-mcp's own local workflow-version storage, not a normal n8n API capability.

## Impact

An authenticated MCP HTTP tenant could read or delete workflow-version backups stored in the default (single-tenant) scope — for example backups left from a prior single-tenant deployment or a migration period. Workflow snapshots may contain sensitive workflow configuration depending on their contents. Single-tenant and stdio deployments are not affected.

## Affected versions

`<= 2.57.3`

## Patched version

`2.57.4`

## Remediation

Upgrade to n8n-mcp `2.57.4` or later. The fix requires a complete tenant context in multi-tenant mode and fails closed for workflow-version access that cannot be attributed to a specific tenant.

## Workarounds

- Restrict network access to the HTTP endpoint (firewall / reverse proxy / VPN) so only trusted callers can reach it. - Run in stdio mode, which has no multi-tenant HTTP surface. - If default-scope backups from a prior single-tenant deployment are not needed, removing them eliminates the exposure.

## Credit

Reported by @DavidCarliez.

CVE-2026-55608 — n8n-MCP: Incorrect authorization can expose default-scope workflow version backups in multi-tenant HTTP mode

Affected: czlonkowski n8n-mcp

n8n-MCP is an MCP server that provides AI assistants access to n8n node documentation, properties, and operations. Prior to 2.57.4, multi-tenant HTTP mode with ENABLE_MULTI_TENANT=true could allow an authenticated tenant to access default-scope workflow_versions backups instead of being confined to the tenant scope, exposing or deleting workflow-version backups from prior single-tenant deployments or migrations. This issue is fixed in version 2.57.4.

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BREW-n8n-mcp-CVE-2026-55608 — n8n-MCP: Incorrect authorization can expose default-scope workflow version backups in multi-tenant HTTP mode

CVE-2026-55608 — n8n-MCP: Incorrect authorization can expose default-scope workflow version backups in multi-tenant HTTP mode