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CVE-2026-81315

Estado: AplazadaAlta (7.4)—

Origin Validation Error vulnerability in ash-project ash_ai allows a malicious web page to bypass the MCP server's DNS-rebinding protection and issue cross-site requests to a user's local MCP server with that user's actor.

In AshAi.Mcp.Server, with the default allowed_origins: nil, origin_allowed?/3 accepts an origin when uri.host == conn.host and the forwarded scheme is https. Both values are attacker-controlled: conn.host comes from the Host header and the scheme is read from the raw x-forwarded-proto header with no trusted-proxy check.

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Under DNS rebinding the browser sends the attacker's origin and a matching host, and page JavaScript may set X-Forwarded-Proto: https, so the check passes with no TLS or proxy involved. The fix trusts only localhost origins by default; other origins require an explicit allowed_origins allowlist.

This issue affects ash_ai: from 0.8.0 before 1.0.0.

CVSS

Probabilidad de explotación (EPSS)

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.

Inferido por reglas deterministas a partir del vector CVSS y la CWE. Solo orientativo.

🛡️ Mitigaciones ATT&CK que cubren estas técnicas

Application Isolation and SandboxingExploit ProtectionUpdate Software

Tecnologías afectadas (1)

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

Ash-project — ASH AIAI

CWE

Referencias

JSON original (NVD)

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{
  "id": "CVE-2026-81315",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-81315",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-08-31T16:02:11.016935Z"
        }
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    "cvssMetricV40": [
      {
        "type": "Secondary",
        "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
        "cvssData": {
          "Safety": "NOT_DEFINED",
          "version": "4.0",
          "Recovery": "NOT_DEFINED",
          "baseScore": 7.4,
          "Automatable": "NOT_DEFINED",
          "attackVector": "NETWORK",
          "baseSeverity": "HIGH",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/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",
          "exploitMaturity": "NOT_DEFINED",
          "providerUrgency": "NOT_DEFINED",
          "userInteraction": "ACTIVE",
          "attackComplexity": "LOW",
          "attackRequirements": "PRESENT",
          "privilegesRequired": "NONE",
          "subIntegrityImpact": "NONE",
          "vulnIntegrityImpact": "HIGH",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "subAvailabilityImpact": "NONE",
          "vulnAvailabilityImpact": "NONE",
          "availabilityRequirement": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "subConfidentialityImpact": "NONE",
          "vulnConfidentialityImpact": "HIGH",
          "confidentialityRequirement": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "vulnerabilityResponseEffort": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED"
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  "affected": [
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      "affectedData": [
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          "cpes": [
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          "repo": "https://github.com/ash-project/ash_ai",
          "vendor": "ash-project",
          "modules": [
            "'Elixir.AshAi.Mcp.Server'"
          ],
          "product": "ash_ai",
          "versions": [
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              "version": "0.8.0",
              "lessThan": "1.0.0",
              "versionType": "semver"
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          "packageURL": "pkg:hex/ash_ai",
          "packageName": "ash_ai",
          "programFiles": [
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          ],
          "collectionURL": "https://repo.hex.pm",
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          "programRoutines": [
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              "name": "'Elixir.AshAi.Mcp.Server':check_origin/2"
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            }
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        {
          "cpes": [
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          "vendor": "ash-project",
          "modules": [
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          "versions": [
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              "versionType": "git"
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          "packageURL": "pkg:github/ash-project/ash_ai",
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          "programFiles": [
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          "collectionURL": "https://github.com",
          "defaultStatus": "unaffected",
          "programRoutines": [
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              "name": "'Elixir.AshAi.Mcp.Server':check_origin/2"
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              "name": "'Elixir.AshAi.Mcp.Server':origin_allowed?/3"
            }
          ]
        }
      ]
    }
  ],
  "published": "2026-08-31T01:16:49.977",
  "references": [
    {
      "url": "https://cna.erlef.org/cves/CVE-2026-81315.html",
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
    },
    {
      "url": "https://github.com/ash-project/ash_ai/commit/28af68d73134df0b8fb3aa6ab03e8fd795b07c21",
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
    },
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      "url": "https://github.com/ash-project/ash_ai/security/advisories/GHSA-c92r-f3rr-q49h",
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
    },
    {
      "url": "https://osv.dev/vulnerability/EEF-CVE-2026-81315",
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
    },
    {
      "url": "https://github.com/ash-project/ash_ai/security/advisories/GHSA-c92r-f3rr-q49h",
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0"
    }
  ],
  "vulnStatus": "Deferred",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "description": [
        {
          "lang": "en",
          "value": "CWE-346"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "Origin Validation Error vulnerability in ash-project ash_ai allows a malicious web page to bypass the MCP server's DNS-rebinding protection and issue cross-site requests to a user's local MCP server with that user's actor.\n\nIn AshAi.Mcp.Server, with the default allowed_origins: nil, origin_allowed?/3 accepts an origin when uri.host == conn.host and the forwarded scheme is https. Both values are attacker-controlled: conn.host comes from the Host header and the scheme is read from the raw x-forwarded-proto header with no trusted-proxy check. Under DNS rebinding the browser sends the attacker's origin and a matching host, and page JavaScript may set X-Forwarded-Proto: https, so the check passes with no TLS or proxy involved. The fix trusts only localhost origins by default; other origins require an explicit allowed_origins allowlist.\n\nThis issue affects ash_ai: from 0.8.0 before 1.0.0."
    }
  ],
  "lastModified": "2026-09-01T21:15:00.147",
  "sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
}