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high · CVSS 8.6

CVE-2026-61542

Gearboy advisory / Gearsystem body: Unauthenticated network exposure of MCP HTTP tools

Published 28 Oct 2026 · Source updated 3 Nov 2026 · Retrieved 2026-11-04 17:07 UTC · This record may be stale; verify the source

Statance checks for CVE-2026-61542. Connected servers are checked automatically against the fixed versions their distribution or package ecosystem has published for it, including app dependency lockfiles. Check my servers ↗
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What happened?

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.

Description supplied by CVE Program. Formatting is simplified; follow the original advisory for full details.

Affected software and versions

Source-provided software and version information
SoftwareVersion informationFixed version
Gearboydrheliusaffected: < 3.8.7See vendor advisory

Version information comes from the source record and can include unaffected products and exceptions. Distribution packages may contain backported fixes: an older upstream version alone does not prove a server is affected.

Is it being exploited?

This CVE was not listed in the CISA catalogue at our last retrieval. This does not establish that exploitation is absent.

CISA data retrieved 2026-11-06 16:38 UTC. Check CISA ↗

How to respond

  1. Confirm the product, installed package version, and any configuration requirements in the vendor advisory.
  2. Follow the vendor’s remediation or workaround guidance in the references below. Structured fixed-version data is unavailable here; the publisher’s description may include a fix or workaround.
  3. Restart affected services if required, then verify the running version. Known exploitation may warrant investigation as well as patching.

Sources and remediation references

This public advisory does not determine whether a particular server is affected. Records are refreshed as sources change; verify urgent decisions against the original advisory.

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