CVE-2026-81094: Missing Auth (CVSS 9.1)

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.

Is your site exposed to CVE-2026-81094?

Run a free security scan — no signup, results in seconds.

CVSS v3.1 Score

9.1

CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

EPSS — Exploit Prediction

0.0042

Probability of exploitation

0.36%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-306 Missing Authentication

References

Other References

https://github.com/mcp-router/mcp-router https://github.com/mcp-router/mcp-router/blob/v0.6.3/apps/cli/src/commands/serve.ts#L105 https://github.com/mcp-router/mcp-router/commit/4c4642cfd274097ec8b33ecd3047390829c79d35 https://github.com/mcp-router/mcp-router/security/advisories/GHSA-rx55-5c7h-r56r https://www.vulncheck.com/advisories/mcp-router-cli-before-0.6.3-binds-the-mcp-aggregator-to-all-interfaces-without-requiring-authentication

Frequently Asked Questions

What is CVE-2026-81094? +

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. It has a CVSS v3.1 base score of 9.1 (CRITICAL).

How severe is CVE-2026-81094? +

CVE-2026-81094 has a CVSS v3.1 score of 9.1 out of 10, rated CRITICAL. This is a critical vulnerability that should be patched immediately. The EPSS score is 0.0042, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-81094? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Related Vulnerabilities

CVE-2026-6369

An improper access control vulnerability in the canonical-livepatch snap client prior to version 10.15.0 allows a local unprivileged user to …

CVE-2026-9152

A missing authentication vulnerability exists in the Altium 365 SearchService. A legacy SOAP endpoint exposes search index operations without requiring …

CVE-2026-5749

Inadequate access control in the registration process in Fullstep V5, which could allow unauthenticated users to obtain a valid JWT …

CVE-2026-6376

A weakness in SpiceJet’s public booking retrieval page permits full passenger booking details to be accessed using only a PNR …

CVE-2024-45483

A Missing Authentication for Critical Function vulnerability in the GRUB configuration used B&R APROL <4.4-01 may allow an unauthenticated physical …

CVE-2024-54013

Penetration Testing engineers at Amazon have identified a security flaw related to request handling in the web server component that …

CVE-2026-81094