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CVE-2026-76172

Estado: AnalizadaAlta (7.5)—

fast-uri is a URI parser for Node.js. During parsing it runs a legacy decoding pass over the scheme component and never re-escapes the result, and serialization writes the scheme back out verbatim, unlike the host component which is re-escaped. As a result an input whose scheme carries percent-encoded slashes parses as a scheme with no authority, so the parsed host and error are both undefined, yet resolving or normalizing that same input emits a network-path reference whose authority is attacker-chosen and re-parses to that host.

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An application that allowlists on the parsed host, or treats a reference with no authority as safe to resolve against its base, gets the opposite of what it checked, giving an off-site redirect, server-side request forgery, or address-policy bypass. The legacy decoder also expands non-standard escape forms, widening the issue past upstream filters, and control characters in the scheme can reach the output as raw carriage return and line feed. The affected versions are 2.3.1 up to but not including 2.4.5, 3.0.0 up to but not including 3.1.6, and 4.0.0 up to but not including 4.1.3. The issue is fixed in 2.4.5, 3.1.6, and 4.1.3, which reject a scheme that is not valid after decoding. Users should upgrade to a patched version.

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.

URI parser flaw en Node.js (AV:N, PR:N) permite SSRF y redirecciones fuera de sitio mediante esquemas malformados que eluden validación de host. Manipulación de datos (I:H) por inyección de componentes en la URL.

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

Filter Network TrafficNetwork SegmentationNetwork Intrusion PreventionLimit Access to Resource Over NetworkEncrypt Sensitive InformationVulnerability Scanning

Tecnologías afectadas (1)

Openjsf — Fast-uri

CWE

Referencias

JSON original (NVD)

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{
  "id": "CVE-2026-76172",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-76172",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-08-24T14:29:20.006884Z"
        }
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "ce714d77-add3-4f53-aff5-83d477b104bb",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 7.5,
          "attackVector": "NETWORK",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "NONE",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "NONE"
        },
        "impactScore": 3.6,
        "exploitabilityScore": 3.9
      }
    ]
  },
  "affected": [
    {
      "source": "ce714d77-add3-4f53-aff5-83d477b104bb",
      "affectedData": [
        {
          "vendor": "fast-uri",
          "product": "fast-uri",
          "versions": [
            {
              "status": "affected",
              "version": "2.3.1",
              "lessThan": "2.4.5",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "2.4.5",
              "versionType": "semver"
            },
            {
              "status": "affected",
              "version": "3.0.0",
              "lessThan": "3.1.6",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "3.1.6",
              "versionType": "semver"
            },
            {
              "status": "affected",
              "version": "4.0.0",
              "lessThan": "4.1.3",
              "versionType": "semver"
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              "status": "unaffected",
              "version": "4.1.3",
              "versionType": "semver"
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          ],
          "packageURL": "pkg:npm/fast-uri",
          "defaultStatus": "unaffected"
        }
      ]
    }
  ],
  "published": "2026-08-24T11:16:40.723",
  "references": [
    {
      "url": "https://cna.openjsf.org/security-advisories.html",
      "tags": [
        "Vendor Advisory"
      ],
      "source": "ce714d77-add3-4f53-aff5-83d477b104bb"
    },
    {
      "url": "https://github.com/fastify/fast-uri/security/advisories/GHSA-jqff-g426-hqxp",
      "tags": [
        "Vendor Advisory"
      ],
      "source": "ce714d77-add3-4f53-aff5-83d477b104bb"
    }
  ],
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "ce714d77-add3-4f53-aff5-83d477b104bb",
      "description": [
        {
          "lang": "en",
          "value": "CWE-177"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "fast-uri is a URI parser for Node.js. During parsing it runs a legacy decoding pass over the scheme component and never re-escapes the result, and serialization writes the scheme back out verbatim, unlike the host component which is re-escaped. As a result an input whose scheme carries percent-encoded slashes parses as a scheme with no authority, so the parsed host and error are both undefined, yet resolving or normalizing that same input emits a network-path reference whose authority is attacker-chosen and re-parses to that host. An application that allowlists on the parsed host, or treats a reference with no authority as safe to resolve against its base, gets the opposite of what it checked, giving an off-site redirect, server-side request forgery, or address-policy bypass. The legacy decoder also expands non-standard escape forms, widening the issue past upstream filters, and control characters in the scheme can reach the output as raw carriage return and line feed. The affected versions are 2.3.1 up to but not including 2.4.5, 3.0.0 up to but not including 3.1.6, and 4.0.0 up to but not including 4.1.3. The issue is fixed in 2.4.5, 3.1.6, and 4.1.3, which reject a scheme that is not valid after decoding. Users should upgrade to a patched version."
    }
  ],
  "lastModified": "2026-09-02T14:43:42.770",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
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              "versionEndExcluding": "2.4.5",
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            },
            {
              "criteria": "cpe:2.3:a:openjsf:fast-uri:*:*:*:*:*:node.js:*:*",
              "vulnerable": true,
              "matchCriteriaId": "1AC6ED82-63FA-4FF2-BB90-48BBBB9A0653",
              "versionEndExcluding": "3.1.6",
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            },
            {
              "criteria": "cpe:2.3:a:openjsf:fast-uri:*:*:*:*:*:node.js:*:*",
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              "matchCriteriaId": "E5821EBB-01F8-44C6-8EFF-BA388AB307D5",
              "versionEndExcluding": "4.1.3",
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          "operator": "OR"
        }
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  "sourceIdentifier": "ce714d77-add3-4f53-aff5-83d477b104bb"
}