CVE-2026-81091

Estado: AplazadaAlta (8.7)—

The proxy middleware in mcp-use's inspector forwards requests to a destination the caller names. mountMcpProxy in libraries/typescript/packages/inspector/src/server/proxy/mcp-proxy.ts read the target from the X-Target-URL header or the __mcp_target parameter and proxied to it without inspecting the host, so loopback, link-local and private addresses were all accepted, as were names that resolve to them, and the validation was not reapplied to a redirect the destination returned.

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A caller could therefore make the server issue requests to addresses reachable only from the host it runs on and read the responses. The current code calls isSafeProxyTarget, which checks the resolved address against private, loopback and link-local ranges before proxying and bounds the number of redirects followed.

CVSS

Versión: 4.0
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Puntuación base: 8.7

Probabilidad de explotación (EPSS)

Probabilidad de explotación en los próximos 30 días: 0.47%
Percentil entre todas las CVEs puntuadas: 38
Fecha de la puntuación: 5/10/2026

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.

ExplotaciónT1190 Exploit Public-Facing Applicationinitial access85 %
Impacto principalT1090.001 Internal Proxycommand and control90 %
Impacto secundarioT1005 Data from Local Systemcollection75 %

Middleware proxy sin validación en AV:N/PR:N permite acceso no autenticado a direcciones privadas (SSRF). Lectura de respuestas desde hosts internos confirmada.

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

Vulnerability Scanning Privileged Account Management Network Segmentation Network Intrusion Prevention Limit Access to Resource Over Network Filter Network Traffic

Tecnologías afectadas (1)

⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.

Mcp-use — Inspector^AI

CWE

CWE-918

Referencias

JSON original (NVD)

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  "id": "CVE-2026-81091",
  "cveTags": [],
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        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-81091",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
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          "version": "2.0.3",
          "timestamp": "2026-08-27T18:12:16.289778Z"
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          "integrityImpact": "NONE",
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          "attackComplexity": "LOW",
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        "exploitabilityScore": 3.9
      }
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          "version": "4.0",
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          "Automatable": "NOT_DEFINED",
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          "valueDensity": "NOT_DEFINED",
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          "vulnIntegrityImpact": "NONE",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
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          "vulnAvailabilityImpact": "NONE",
          "availabilityRequirement": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
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          "vulnerabilityResponseEffort": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED"
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          "vendor": "mcp-use",
          "product": "mcp-use",
          "versions": [
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              "version": "0",
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  "published": "2026-08-27T17:20:51.183",
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      "url": "https://github.com/mcp-use/mcp-use/security/advisories/GHSA-f2jg-rm2x-hc5p",
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      "url": "https://www.vulncheck.com/advisories/mcp-use-inspector-proxy-server-side-request-forgery-via-caller-supplied-target-url",
      "source": "disclosure@vulncheck.com"
    }
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      "description": [
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          "value": "CWE-918"
        }
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  ],
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    {
      "lang": "en",
      "value": "The proxy middleware in mcp-use's inspector forwards requests to a destination the caller names. mountMcpProxy in libraries/typescript/packages/inspector/src/server/proxy/mcp-proxy.ts read the target from the X-Target-URL header or the __mcp_target parameter and proxied to it without inspecting the host, so loopback, link-local and private addresses were all accepted, as were names that resolve to them, and the validation was not reapplied to a redirect the destination returned. A caller could therefore make the server issue requests to addresses reachable only from the host it runs on and read the responses. The current code calls isSafeProxyTarget, which checks the resolved address against private, loopback and link-local ranges before proxying and bounds the number of redirects followed."
    }
  ],
  "lastModified": "2026-09-23T17:17:43.387",
  "sourceIdentifier": "disclosure@vulncheck.com"
}