Attack Chain

1. The victim visits an attacker-controlled website which initiates a DNS rebinding sequence against an internal or localhost domain.
2. The browser is directed to resolve a malicious domain to 127.0.0.1, bypassing the Same-Origin Policy.
3. The malicious website sends a crafted HTTP POST request to the local genieacs-mcp listener at 127.0.0.1:8080/mcp.
4. The genieacs-mcp server processes the request without verifying the Host or Origin headers, assuming the loopback traffic is benign.
5. The attacker initializes an MCP session by sending a JSON-RPC initialize request, receiving a session ID.
6. The attacker invokes administrative tools such as get_parameter or reboot_device via tools/call.
7. The genieacs-mcp backend relays these authenticated tool calls to the target GenieACS NBI, leading to unauthorized device management actions.

Impact

Successful exploitation allows a remote attacker to act as an authenticated user of the GenieACS MCP interface. This results in unauthorized control over device fleets, including the ability to reboot CPE devices, initiate firmware downloads, and modify TR-069 device parameters. Exposure of these management interfaces presents a significant risk to the integrity and availability of the managed network devices.

Recommendation

1. Upgrade genieacs-mcp to a version that enforces strict Host and Origin header validation for all HTTP transport requests, including loopback.
2. For current deployments, implement a reverse proxy or WAF layer that rejects requests to the MCP endpoint if the Host and Origin headers do not match expected local values (e.g., 127.0.0.1:8080 or localhost:8080).
3. Require a bearer token for all HTTP transport configurations, even for local loopback interfaces, to mitigate the risk of unauthenticated requests.
4. Consider migrating to the stdio transport mode if HTTP-based MCP bridging is not strictly required for the specific integration.