CVE-2026-81094 PUBLISHED

mcp-router CLI before 0.6.3 Binds the MCP Aggregator to All Interfaces Without Requiring Authentication

Assigner: VulnCheck
Reserved: 26.08.2026 Published: 27.08.2026 Updated: 27.08.2026

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.

Metrics

CVSS Vector: 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
CVSS Score: 9.3

Product Status

Vendor mcp-router
Product mcp-router
Versions Default: unaffected
  • affected from 0 to 0.6.3 (excl.)
  • Version 4c4642cfd274097ec8b33ecd3047390829c79d35 is unaffected

Credits

  • Yotam Perkal (Pluto Security) finder

References

Problem Types

  • Missing Authentication for Critical Function CWE