Gearboy is a Game Boy, Game Boy Color, and Super Game Boy emulator and debugger with an embedded MCP server. Gearsystem, the affected component, has an optional `--mcp-http` mode that accepts unauthenticated MCP requests from any reachable network peer despite localhost-only documentation and logging. In the described `platforms/shared/desktop/mcp/mcp_transport.h` transport, the socket binds `INADDR_ANY`, normally on port 7777, and POST requests to `/mcp` reach dispatch without `Authorization`, `Host`, or `Origin` checks. Responses and OPTIONS advertise `Access-Control-Allow-Origin: *`. A peer can initialize an MCP session and invoke exposed emulator/debugging operations; even a garbage bearer token does not block dispatch, while a loopback-bind negative control prevents network access. The reported impact is bounded to the emulator process, debugging state, and local files accepted as media, rather than demonstrated host code execution. Gearboy 3.8.7 contains a patch.
History

Tue, 03 Nov 2026 15:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Wed, 28 Oct 2026 22:15:00 +0000

Type Values Removed Values Added
First Time appeared Drhelius
Drhelius gearboy
Vendors & Products Drhelius
Drhelius gearboy

Wed, 28 Oct 2026 20:00:00 +0000

Type Values Removed Values Added
Description Gearboy is a Game Boy, Game Boy Color, and Super Game Boy emulator and debugger with an embedded MCP server. Gearsystem, the affected component, has an optional `--mcp-http` mode that accepts unauthenticated MCP requests from any reachable network peer despite localhost-only documentation and logging. In the described `platforms/shared/desktop/mcp/mcp_transport.h` transport, the socket binds `INADDR_ANY`, normally on port 7777, and POST requests to `/mcp` reach dispatch without `Authorization`, `Host`, or `Origin` checks. Responses and OPTIONS advertise `Access-Control-Allow-Origin: *`. A peer can initialize an MCP session and invoke exposed emulator/debugging operations; even a garbage bearer token does not block dispatch, while a loopback-bind negative control prevents network access. The reported impact is bounded to the emulator process, debugging state, and local files accepted as media, rather than demonstrated host code execution. Gearboy 3.8.7 contains a patch.
Title Gearboy advisory / Gearsystem body: Unauthenticated network exposure of MCP HTTP tools
Weaknesses CWE-306
References
Metrics cvssV3_1

{'score': 8.6, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:L'}


cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published: 2026-10-28T19:48:42.991Z

Updated: 2026-11-03T14:11:09.339Z

Reserved: 2026-07-10T16:27:03.093Z

Link: CVE-2026-61542

cve-icon Vulnrichment

Updated: 2026-11-03T14:07:04.856Z

cve-icon NVD

Status : Deferred

Published: 2026-10-28T20:18:27.213

Modified: 2026-11-03T14:17:36.710

Link: CVE-2026-61542

cve-icon Redhat

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