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FKIE_CVE-2026-59973

Vulnerability from fkie_nvd - Published: 2026-09-15 16:17 - Updated: 2026-09-16 17:17
Severity
8.5 (High) - CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N
Summary
FrontMCP is a TypeScript-first framework for the Model Context Protocol (MCP). From mcp-from-openapi 2.3.0 until 2.5.0 and from frontmcp and @frontmcp/adapters 1.2.1 until 1.5.0, libs/adapters/src/openapi/openapi.adapter.ts loadOpenAPISpec() forwards untrusted OpenAPI url and spec inputs and loadOptions.refResolution to OpenAPIToolGenerator.fromURL() and OpenAPIToolGenerator.fromJSON(). The external $ref guard checks parsed hostname strings without resolving addresses, pinning validated addresses, revalidating redirect targets, or normalizing IPv4-mapped IPv6. An authenticated user who can import or configure an OpenAPI specification in a hosted or multi-user deployment can use DNS-to-loopback resolution, redirect-to-loopback behavior, or IPv4-mapped IPv6 loopback forms to cause backend-origin requests to internal services. This can expose internal administrative APIs, metadata-like services, and other private network endpoints. The practical impact is lower when only a trusted local administrator can configure OpenAPI specs, and disabling external reference protocols prevents the external $ref request. This issue is fixed in mcp-from-openapi 2.5.0 and frontmcp and @frontmcp/adapters 1.5.0.
References
security-advisories@github.comhttps://github.com/agentfront/frontmcp/commit/96a78eaa5c6c4bc51cced557d83d1a03344cb03d
security-advisories@github.comhttps://github.com/agentfront/frontmcp/pull/496
security-advisories@github.comhttps://github.com/agentfront/frontmcp/releases/tag/v1.5.0
security-advisories@github.comhttps://github.com/agentfront/frontmcp/security/advisories/GHSA-65h7-9wrw-629c
security-advisories@github.comhttps://github.com/agentfront/mcp-from-openapi/commit/be3409cce6e97642696d4ee5a4e4e2712490b277
security-advisories@github.comhttps://github.com/agentfront/mcp-from-openapi/pull/7
security-advisories@github.comhttps://github.com/agentfront/mcp-from-openapi/releases/tag/v2.5.0
134c704f-9b21-4f2e-91b3-4a467353bcc0https://github.com/agentfront/frontmcp/security/advisories/GHSA-65h7-9wrw-629c
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "frontmcp",
          "vendor": "agentfront",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 1.5.0"
            }
          ]
        },
        {
          "product": "mcp-from-openapi",
          "vendor": "agentfront",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 2.5.0"
            }
          ]
        },
        {
          "product": "adapters",
          "vendor": "@frontmcp",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 1.5.0"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "FrontMCP is a TypeScript-first framework for the Model Context Protocol (MCP). From mcp-from-openapi 2.3.0 until 2.5.0 and from frontmcp and @frontmcp/adapters 1.2.1 until 1.5.0, libs/adapters/src/openapi/openapi.adapter.ts loadOpenAPISpec() forwards untrusted OpenAPI url and spec inputs and loadOptions.refResolution to OpenAPIToolGenerator.fromURL() and OpenAPIToolGenerator.fromJSON(). The external $ref guard checks parsed hostname strings without resolving addresses, pinning validated addresses, revalidating redirect targets, or normalizing IPv4-mapped IPv6. An authenticated user who can import or configure an OpenAPI specification in a hosted or multi-user deployment can use DNS-to-loopback resolution, redirect-to-loopback behavior, or IPv4-mapped IPv6 loopback forms to cause backend-origin requests to internal services. This can expose internal administrative APIs, metadata-like services, and other private network endpoints. The practical impact is lower when only a trusted local administrator can configure OpenAPI specs, and disabling external reference protocols prevents the external $ref request. This issue is fixed in mcp-from-openapi 2.5.0 and frontmcp and @frontmcp/adapters 1.5.0."
    }
  ],
  "id": "CVE-2026-59973",
  "lastModified": "2026-09-16T17:17:28.750",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 8.5,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "LOW",
          "privilegesRequired": "LOW",
          "scope": "CHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 3.1,
        "impactScore": 4.7,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-59973",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-09-16T16:06:47.172118Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-09-15T16:17:18.327",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/agentfront/frontmcp/commit/96a78eaa5c6c4bc51cced557d83d1a03344cb03d"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/agentfront/frontmcp/pull/496"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/agentfront/frontmcp/releases/tag/v1.5.0"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/agentfront/frontmcp/security/advisories/GHSA-65h7-9wrw-629c"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/agentfront/mcp-from-openapi/commit/be3409cce6e97642696d4ee5a4e4e2712490b277"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/agentfront/mcp-from-openapi/pull/7"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/agentfront/mcp-from-openapi/releases/tag/v2.5.0"
    },
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "url": "https://github.com/agentfront/frontmcp/security/advisories/GHSA-65h7-9wrw-629c"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Received",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-918"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}



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