VULNpocalypse

CVE-2026-55605: @arikusi/deepseek-mcp-server Missing Authentication on Self-Hosted HTTP MCP Endpoint

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

DeepSeek MCP Server is an MCP server for DeepSeek V4. Starting in version 1.4.2 and prior to version 1.8.0, the self-hosted HTTP transport of `@arikusi/deepseek-mcp-server` exposes `POST /mcp` without any authentication: `createMcpExpressApp` is called without an `authProvider` and no middleware guards the route, so any network-reachable client can issue an unauthenticated `initialize` request and obtain a valid MCP session identifier. In reproduced testing against commit `5e1302171e99`, an unauthenticated client was able to initialize a session, enumerate tools, and invoke the local `deepseek_sessions` tool with no credentials. The same unauthenticated session also exposes `deepseek_chat`, whose handler uses the server-side `DEEPSEEK_API_KEY` when self-hosted deployments configure one. This issue applies to self-hosted HTTP mode, not the separately documented hosted BYOK endpoint in `README.md`, which expects an `Authorization: Bearer ...` header. Upstream self-hosted container assets enable HTTP mode by default (`Dockerfile`) and publish port `3000` (`docker-compose.yml`). Version 1.8.0 contains a patch for this issue.

Description quoted from the CVE record (assigned by GitHub_M, published 2026-07-09).

Weakness: CWE-306: Missing Authentication for Critical Function

How it can be exploited

Exploitable over the network with low attack complexity needing no privileges and no user interaction. Impact: confidentiality none, integrity none, availability low. CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

CISA assessment (SSVC): CISA assesses that a public proof of concept exists. Automatable: yes. Technical impact: partial.

Public exploit evidence (Exploit Observer)

Also known as: EUVD-2026-42717, GHSA-72f3-6w86-7rv3

VEDAS cluster: VEDAS:DELICATEDIANA

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 (5)

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
0.005
low predicted chance of attack
VEDAS
0.987
strong exploit evidence
On CISA KEV
Not listed
Detection rule
Nuclei · Suricata

Who is affected

ProductAffectedNot affected
arikusi deepseek-mcp-serverversion >= 1.4.2, < 1.8.0Not stated

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

How to fix it

No fixed version or vendor advisory is listed in the CVE record yet. Watch the vendor’s security page.

How to detect it

Nuclei template (active check)

DeepSeek MCP Server - Missing Authentication on /mcp

The self-hosted HTTP transport of @arikusi/deepseek-mcp-server from 1.4.2 before 1.8.0 exposes POST /mcp with no authentication: createMcpExpressApp is called without an authProvider and no middleware guards the route, so any network-reachable client can complete an MCP initialize handshake and obtain a session with no credentials. This template sends an unauthenticated JSON-RPC initialize request and confirms the server returns a valid MCP initialize result.

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

The template sends 1 request (POST /mcp); it decides using status, word matchers. Severity in the template: medium. 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-2026-55605.yaml
Show the template (45 lines)
yaml
id: CVE-2026-55605

info:
  name: "DeepSeek MCP Server - Missing Authentication on /mcp"
  author: vedas-arpsyndicate
  severity: medium
  description: |
    The self-hosted HTTP transport of @arikusi/deepseek-mcp-server from 1.4.2 before 1.8.0 exposes
    POST /mcp with no authentication: createMcpExpressApp is called without an authProvider and no
    middleware guards the route, so any network-reachable client can complete an MCP initialize
    handshake and obtain a session with no credentials. This template sends an unauthenticated
    JSON-RPC initialize request and confirms the server returns a valid MCP initialize result.
  reference:
    - https://www.exploit.observer/?keyword=CVE-2026-55605&match=exact
    - https://subdomain.center/?engine=ammonites&keyword=deepseek&match=exact
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
    cvss-score: 5.3
    cve-id: CVE-2026-55605
    cwe-id: CWE-306
  metadata:
    verified: false
  tags: cve,cve2026,deepseek,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":"2024-11-05","capabilities":{},"clientInfo":{"name":"vedas-check","version":"1.0"}}}

    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        part: body
        words:
          - '"protocolVersion"'
          - '"serverInfo"'
        condition: and

CVE-2026-55605.yaml on GitHub

Suricata rules (network detection)

1 rule that alert on traffic matching this exploit: VEDAS CVE-2026-55605 DeepSeek MCP Server - Unauthenticated /mcp Initialize. Add them to your Suricata rule set and reload.

Show the rules
suricata
alert http $EXTERNAL_NET any -> $HTTP_SERVERS $HTTP_PORTS (msg:"VEDAS CVE-2026-55605 DeepSeek MCP Server - Unauthenticated /mcp Initialize"; flow:established,to_server; http.method; content:"POST"; http.uri; content:"/mcp"; http.request_body; content:"initialize"; fast_pattern; content:"protocolVersion"; classtype:web-application-attack; reference:cve,CVE-2026-55605; reference:url,https://www.exploit.observer/?keyword=CVE-2026-55605&match=exact; reference:url,https://subdomain.center/?engine=ammonites&keyword=deepseek&match=exact; sid:1081807; rev:1;)

CVE-2026-55605.rules on GitHub

References

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.