CVE-2026-61542 (GCVE-0-2026-61542)

Vulnerability from cvelistv5 – Published: 2026-10-28 19:48 – Updated: 2026-10-28 19:48
VLAI
Title
Gearboy advisory / Gearsystem body: Unauthenticated network exposure of MCP HTTP tools
Summary
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.
Severity
8.6 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:L
CWE
  • CWE-306 - Missing Authentication for Critical Function
Assigner
GitHub_M CNA under the mitre root
CNA scorecard C 72/100 over 8129 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
drhelius Gearboy Affected: < 3.8.7
guessed Create a notification for this product.
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{
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        {
          "product": "Gearboy",
          "vendor": "drhelius",
          "versions": [
            {
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              "version": "\u003c 3.8.7"
            }
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        {
          "lang": "en",
          "value": "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."
        }
      ],
      "metrics": [
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            "baseSeverity": "HIGH",
            "confidentialityImpact": "LOW",
            "integrityImpact": "HIGH",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:L",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-306",
              "description": "CWE-306: Missing Authentication for Critical Function",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-28T19:48:42.991Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
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          "name": "https://github.com/drhelius/Gearboy/security/advisories/GHSA-fmvx-487g-mrww",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/drhelius/Gearboy/security/advisories/GHSA-fmvx-487g-mrww"
        },
        {
          "name": "https://github.com/drhelius/Gearboy/commit/e2ead98e2fac41e9df5a499e9e421c6a0e73f1bc",
          "tags": [
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          "url": "https://github.com/drhelius/Gearboy/commit/e2ead98e2fac41e9df5a499e9e421c6a0e73f1bc"
        },
        {
          "name": "https://github.com/drhelius/Gearboy/releases/tag/3.8.7",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/drhelius/Gearboy/releases/tag/3.8.7"
        }
      ],
      "source": {
        "advisory": "GHSA-fmvx-487g-mrww",
        "discovery": "UNKNOWN"
      },
      "title": "Gearboy advisory / Gearsystem body: Unauthenticated network exposure of MCP HTTP tools"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-61542",
    "datePublished": "2026-10-28T19:48:42.991Z",
    "dateReserved": "2026-07-10T16:27:03.093Z",
    "dateUpdated": "2026-10-28T19:48:42.991Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
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      "date": "2026-10-30",
      "epss": "0.00307",
      "percentile": "0.23492"
    },
    "nvd": {
      "cve": {
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              {
                "product": "Gearboy",
                "vendor": "drhelius",
                "versions": [
                  {
                    "status": "affected",
                    "version": "\u003c 3.8.7"
                  }
                ]
              }
            ],
            "source": "security-advisories@github.com"
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "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."
          }
        ],
        "id": "CVE-2026-61542",
        "lastModified": "2026-10-29T16:21:34.310",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "NETWORK",
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                "integrityImpact": "HIGH",
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                "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:L",
                "version": "3.1"
              },
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              "impactScore": 4.7,
              "source": "security-advisories@github.com",
              "type": "Secondary"
            }
          ]
        },
        "published": "2026-10-28T20:18:27.213",
        "references": [
          {
            "source": "security-advisories@github.com",
            "url": "https://github.com/drhelius/Gearboy/commit/e2ead98e2fac41e9df5a499e9e421c6a0e73f1bc"
          },
          {
            "source": "security-advisories@github.com",
            "url": "https://github.com/drhelius/Gearboy/releases/tag/3.8.7"
          },
          {
            "source": "security-advisories@github.com",
            "url": "https://github.com/drhelius/Gearboy/security/advisories/GHSA-fmvx-487g-mrww"
          }
        ],
        "sourceIdentifier": "security-advisories@github.com",
        "vulnStatus": "Deferred",
        "weaknesses": [
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-306"
              }
            ],
            "source": "security-advisories@github.com",
            "type": "Primary"
          }
        ]
      }
    }
  }
}



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