CVE-2026-55605 @arikusi/deepseek-mcp-server Missing Authentication on Self-Hosted HTTP MCP Endpoint
Unauthenticated attackers can access the self-hosted HTTP endpoint to enumerate tools and invoke functions, potentially exposing API keys or executing actions.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-55605?
CVE-2026-55605 is a medium-severity missing authorization vulnerability in arikusi deepseek-mcp-server, published on 9 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Weakness: CWE-306
Which versions are affected by CVE-2026-55605?
2 open source packages ship an affected version, including @arikusi/deepseek-mcp-server.
| Package | Affected | Fixed in |
|---|---|---|
@arikusi/deepseek-mcp-server npm | From 1.4.2 | 1.8.0 |
@arikusi/deepseek-mcp-server npm | From 1.4.2 | 1.8.0 |
How do I fix CVE-2026-55605?
Upgrade @arikusi/deepseek-mcp-server to 1.8.0 or later.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2026-55605 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55605 exists.
Sources
Also known as GHSA-72f3-6w86-7rv3.