---
id: CVE-2026-81094
title: >-
  The mcp-router CLI served its MCP aggregator on every interface and enforced
  authentication only when the operator asked for it
summary: >-
  The mcp-router CLI served its MCP aggregator on every interface and enforced
  authentication only when the operator asked for it. The serve command in
  apps/cli/src/commands/serve.ts defaulted its host to the all-interfaces
  address on a fi…
severity: critical
cvss: 9.1
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N'
cwe:
  - CWE-306
published: '2026-08-27'
updated: '2026-09-23'
sourceUpdated: '2026-09-23T17:17:42.530'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-81094'
references:
  - url: 'https://github.com/mcp-router/mcp-router'
    label: disclosure@vulncheck.com
  - url: >-
      https://github.com/mcp-router/mcp-router/blob/v0.6.3/apps/cli/src/commands/serve.ts#L105
    label: disclosure@vulncheck.com
  - url: >-
      https://github.com/mcp-router/mcp-router/commit/4c4642cfd274097ec8b33ecd3047390829c79d35
    label: disclosure@vulncheck.com
  - url: >-
      https://github.com/mcp-router/mcp-router/security/advisories/GHSA-rx55-5c7h-r56r
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/mcp-router-cli-before-0.6.3-binds-the-mcp-aggregator-to-all-interfaces-without-requiring-authentication
    label: disclosure@vulncheck.com
tags:
  - nvd
epss: 0.00423
epssPercentile: 0.36236
ingestedAt: '2026-09-23T17:28:14.806Z'
---

## Overview

The mcp-router CLI served its MCP aggregator on every interface and enforced authentication only when the operator asked for it. The serve command in apps/cli/src/commands/serve.ts defaulted its host to the all-interfaces address on a fixed port, and required a token only when the corresponding flag was supplied, so a default invocation exposed the aggregator, and every MCP server it fronted, to anyone able to reach the port. Release 0.6.3 defaults the host to the loopback address and refuses to start without a token whenever the host it is given is not a loopback address; no earlier release carries either check.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.