VULNpocalypse

CVE-2026-81094: mcp-router CLI before 0.6.3 Binds the MCP Aggregator to All Interfaces Without Requiring Authentication

Advisory generated from the CVE record, CISA, Exploit Observer and VEDAS: what it is, whether it is exploited, who is affected, and how to fix and detect it.

Generated by VEDAS. Scores as of 2026-11-01 19:19 UTC. Rebuilt every few hours from cve-scores, CISA KEV and vedas-signatures. How this works and its limits.

What it is

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.

Description quoted from the CVE record (assigned by VulnCheck, published 2026-08-27).

Weakness: Missing Authentication for Critical Function

How it can be exploited

Exploitable over the network with low attack complexity with no special attack requirements needing no privileges and no user interaction. Impact: confidentiality high, integrity high, availability none. CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

CISA assessment (SSVC): CISA has no evidence of exploitation. Automatable: yes. Technical impact: total.

Public exploit evidence (Exploit Observer)

Also known as: EUVD-2026-67022, GHSA-g448-x63h-m2m3

VEDAS cluster: VEDAS:DEFTDRAGON

Exploit Observer links 5 pieces of public exploit code or detection modules that name this CVE or one of its aliases.

Exploit code and modules (5)

Code that names this CVE. A repository can be a working exploit, a scanner, a fake or malware; read it before running anything.

Vulnerability databases and vendor advisories (3)

Catalogue entries, not exploit evidence.

2 more references returned by Exploit Observer did not name this CVE or an alias, so they are left out.

VEDAS data as of 2026-11-01T17:12 UTC; fetched 2026-11-02.

Live scores

EPSS
0.006
low predicted chance of attack
VEDAS
0.988
strong exploit evidence
On CISA KEV
Not listed
Detection rule
Nuclei · Suricata

Who is affected

ProductAffectedNot affected
mcp-router mcp-routerbefore 0.6.34c4642cfd274 is not affected

Version ranges exactly as the CVE record states them. “Before X” means X is the first fixed version.

How to fix it

Fixed versions stated in the CVE record: 0.6.3.

Vendor guidance:

How to detect it

Nuclei template (active check)

mcp-router CLI - Unauthenticated MCP Aggregator Exposure

The mcp-router CLI served its MCP aggregator on every interface and required a token only when the operator passed the corresponding flag. The serve command in apps/cli/src/commands/serve.ts defaulted its host to the all-interfaces address on a fixed port, so a default invocation exposed the aggregator, and every MCP server it fronts, to anyone able to reach the port. An unauthenticated attacker can complete the MCP initialize handshake and reach the fronted tools. Fixed in release 0.6.3.

Name and description quoted from the template, written by VEDAS.

The template sends 1 request (POST /mcp); it decides using dsl matchers. Severity in the template: critical. Marked as not yet verified against a live vulnerable target.

Run it against a host you own or are authorised to test:

bash
nuclei -u https://your-host -t CVE-2026-81094.yaml
Show the template (41 lines)
yaml
id: CVE-2026-81094

info:
  name: "mcp-router CLI - Unauthenticated MCP Aggregator Exposure"
  author: vedas-arpsyndicate
  severity: critical
  description: |
    The mcp-router CLI served its MCP aggregator on every interface and required a token only
    when the operator passed the corresponding flag. The serve command in
    apps/cli/src/commands/serve.ts defaulted its host to the all-interfaces address on a fixed
    port, so a default invocation exposed the aggregator, and every MCP server it fronts, to
    anyone able to reach the port. An unauthenticated attacker can complete the MCP initialize
    handshake and reach the fronted tools. Fixed in release 0.6.3.
  reference:
    - https://www.exploit.observer/?keyword=CVE-2026-81094&match=exact
    - https://subdomain.center/?engine=ammonites&keyword=mcp-router&match=exact
  classification:
    cvss-metrics: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H
    cvss-score: 9.3
    cve-id: CVE-2026-81094
    cwe-id: CWE-306
  metadata:
    verified: false
  tags: cve,cve2026,mcp-router,mcp,auth-bypass
http:
  - raw:
      - |
        POST /mcp HTTP/1.1
        Host: {{Hostname}}
        Content-Type: application/json
        Accept: application/json, text/event-stream

        {"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2025-06-18","capabilities":{},"clientInfo":{"name":"mcp","version":"1.0"}}}

    matchers:
      - type: dsl
        dsl:
          - 'contains(body, "protocolVersion")'
          - 'contains(body, "jsonrpc")'
          - 'status_code == 200'
        condition: and

CVE-2026-81094.yaml on GitHub

Suricata rules (network detection)

1 rule that alert on traffic matching this exploit: VEDAS CVE-2026-81094 mcp-router CLI - Unauthenticated MCP Aggregator Handshake Attempt. Add them to your Suricata rule set and reload.

Show the rules
suricata
alert http $EXTERNAL_NET any -> $HOME_NET any (msg:"VEDAS CVE-2026-81094 mcp-router CLI - Unauthenticated MCP Aggregator Handshake Attempt"; flow:established,to_server; http.method; content:"POST"; http.uri; content:"/mcp"; nocase; http.request_body; content:"initialize"; nocase; fast_pattern; content:"jsonrpc"; nocase; classtype:attempted-admin; reference:cve,CVE-2026-81094; reference:url,https://www.exploit.observer/?keyword=CVE-2026-81094&match=exact; reference:url,https://subdomain.center/?engine=ammonites&keyword=mcp-router&match=exact; sid:1081402; rev:1;)

CVE-2026-81094.rules on GitHub

References

Vendor advisories and patches

Exploits and technical analysis

Other references

Other databases

Where this comes from

This advisory is generated automatically by VEDAS from: CVE.org record, cve-scores (EPSS and VEDAS), Exploit Observer, vedas-signatures. Text in quotes is reproduced from the source; everything else is a fixed template filled with source fields. Nothing here is written by a language model. Check the vendor advisory before acting, and read how VEDAS and Exploit Observer work, and their limits.