CVE-2026-55637

Description

genieacs-mcp is an MCP server for GenieACS written in Go. Prior to 0.3.2, the Streamable HTTP transport in cmd/server/main.go creates an unauthenticated /mcp listener on the default MCP_LISTEN_ADDR value 127.0.0.1:8080 when MCP_AUTH_TOKEN is unset and the httpSrv.Start(addr) branch does not validate the Host or Origin headers. A malicious website can use DNS rebinding to send browser requests with attacker-controlled Host and Origin values to the loopback listener, initialize an MCP session, list tools, and invoke operations against the GenieACS NBI configured by ACS_URL. Successful exploitation can expose or modify CPE management state, including device reboots, firmware tasks, TR-069 parameter changes, presets, provisions, tags, connection requests, and task operations. The npm wrapper is not affected because it forces TRANSPORT=stdio and does not expose an HTTP listener. This issue is fixed in version 0.3.2.

References

• https://github.com/GeiserX/genieacs-mcp/commit/577306d78190622eee97e362b042a69499ef373f
• https://github.com/GeiserX/genieacs-mcp/pull/26
• https://github.com/GeiserX/genieacs-mcp/releases/tag/v0.3.2
• https://github.com/GeiserX/genieacs-mcp/security/advisories/GHSA-cmwv-wf9p-p8wx
• https://github.com/GeiserX/genieacs-mcp/security/advisories/GHSA-cmwv-wf9p-p8wx