CVE-2026-81094

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.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of data exposure, data tampering.

Exploit odds

0.6% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-08-27 17:20 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-09-23 17:17 UTC Last updatedMost recent change to the record

Details

Published

2026-08-27 17:20 UTC

Last modified

2026-09-23 17:17 UTC

Exploit probability

0.6% · EPSS, next 30 days

Weakness

CWE-306 · Missing authentication

Record status

Deferred

Attack profile CVSS 4.0 · 9.3

Attack vector

Network

Complexity

Low

Attack requirements

None

Privileges needed

None

User interaction

None

Confidentiality

High

Integrity

High

Availability

None