CVE-2026-59973
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.
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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.
CVSS
- Versión: 3.1
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N
- Puntuación base: 8.5
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.39%
- Percentil entre todas las CVEs puntuadas: 31
- Fecha de la puntuación: 6/10/2026
EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).
🎯 Técnicas ATT&CK
Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.
- Explotación
T1210Exploitation of Remote Serviceslateral movement92 % - Impacto principal
T1090.004Domain Frontingcommand and control88 % - Impacto secundario
T1552.007Container APIcredential access78 %
AV:N/PR:L: acceso remoto con privilegios. CWE-918 (SSRF). Usuario autenticado manipula URL de OpenAPI para redirigir a servicios internos/loopback, exponiendo APIs administrativas y metadatos privados (proxy inverso/SSRF + exfiltración de datos internos).
Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.
🛡️ Mitigaciones ATT&CK que cubren estas técnicas
Tecnologías afectadas (3)
⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.
CWE
- CWE-918
Referencias
- https://github.com/agentfront/frontmcp/commit/96a78eaa5c6c4bc51cced557d83d1a03344cb03d
- https://github.com/agentfront/frontmcp/pull/496
- https://github.com/agentfront/frontmcp/releases/tag/v1.5.0
- https://github.com/agentfront/frontmcp/security/advisories/GHSA-65h7-9wrw-629c
- https://github.com/agentfront/mcp-from-openapi/commit/be3409cce6e97642696d4ee5a4e4e2712490b277
- https://github.com/agentfront/mcp-from-openapi/pull/7
- https://github.com/agentfront/mcp-from-openapi/releases/tag/v2.5.0
- https://github.com/agentfront/frontmcp/security/advisories/GHSA-65h7-9wrw-629c
JSON original (NVD)
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{
"id": "CVE-2026-59973",
"cveTags": [],
"metrics": {
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"id": "CVE-2026-59973",
"role": "CISA Coordinator",
"options": [
{
"exploitation": "poc"
},
{
"automatable": "no"
},
{
"technicalImpact": "partial"
}
],
"version": "2.0.3",
"timestamp": "2026-09-16T16:06:47.172118Z"
}
}
],
"cvssMetricV31": [
{
"type": "Secondary",
"source": "security-advisories@github.com",
"cvssData": {
"scope": "CHANGED",
"version": "3.1",
"baseScore": 8.5,
"attackVector": "NETWORK",
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N",
"integrityImpact": "LOW",
"userInteraction": "NONE",
"attackComplexity": "LOW",
"availabilityImpact": "NONE",
"privilegesRequired": "LOW",
"confidentialityImpact": "HIGH"
},
"impactScore": 4.7,
"exploitabilityScore": 3.1
}
]
},
"affected": [
{
"source": "security-advisories@github.com",
"affectedData": [
{
"vendor": "agentfront",
"product": "frontmcp",
"versions": [
{
"status": "affected",
"version": "< 1.5.0"
}
]
},
{
"vendor": "agentfront",
"product": "mcp-from-openapi",
"versions": [
{
"status": "affected",
"version": "< 2.5.0"
}
]
},
{
"vendor": "@frontmcp",
"product": "adapters",
"versions": [
{
"status": "affected",
"version": "< 1.5.0"
}
]
}
]
}
],
"published": "2026-09-15T16:17:18.327",
"references": [
{
"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": "security-advisories@github.com"
},
{
"url": "https://github.com/agentfront/frontmcp/security/advisories/GHSA-65h7-9wrw-629c",
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0"
}
],
"vulnStatus": "Deferred",
"weaknesses": [
{
"type": "Secondary",
"source": "security-advisories@github.com",
"description": [
{
"lang": "en",
"value": "CWE-918"
}
]
}
],
"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."
}
],
"lastModified": "2026-09-30T17:51:56.193",
"sourceIdentifier": "security-advisories@github.com"
}