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

> The mcp-router CLI defaults to binding on all interfaces without authentication, exposing the MCP aggregator and fronted servers to unauthorized network access.

- **Severity:** Critical 9.3 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 27 Aug 2026
- **Updated:** 29 Aug 2026
- **Also known as:** GHSA-g448-x63h-m2m3, GHSA-rx55-5c7h-r56r

## What is CVE-2026-81094?

CVE-2026-81094 is a critical missing authorization vulnerability in mcp-router, published on 27 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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.

Weakness: CWE-306 (Missing Authentication for Critical Functionality)

## Which versions are affected by CVE-2026-81094?


## How do I fix CVE-2026-81094?

No fix has been published for CVE-2026-81094 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-81094 being exploited?

There is no known exploitation of CVE-2026-81094 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-81094 and fix it if it is affected.

What it is: CVE-2026-81094 is a critical missing authorization vulnerability in mcp-router, published on 27 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-81094 in the wild and no public exploit code.

Affected product: mcp-router. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-81094/ (Markdown: https://insights.sbomify.com/CVE-2026-81094/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-81094
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-81094
- OSV: https://osv.dev/vulnerability/CVE-2026-81094

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-81094/
Summaries are generated and may contain mistakes; the official description above is the record.