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CVE-2026-75931

Estado: AnalizadaAlta (7.5)—

fast-uri is a URI parser for Node.js. It canonicalizes a host to its ASCII form only when the input carries an explicit scheme, so a scheme-relative reference such as a host preceded by two slashes is returned with its host verbatim and no error set. As a result fast-uri's own entry points disagree with each other: parse, resolve, normalize, and equal can yield different hosts for the same input depending only on whether a scheme is written out, and equal can return opposite verdicts for the same pair of hosts.

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An application that extracts a host with fast-uri to check it against a policy list and then resolves the same reference can make its decision on one host while the destination is another, enabling host confusion and policy bypass. The affected versions are 2.4.2 up to but not including 2.4.5, 3.1.3 up to but not including 3.1.6, and 4.0.1 up to but not including 4.1.3. The issue is fixed in 2.4.5, 3.1.6, and 4.1.3, which canonicalize the host consistently across the resolve path. 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.

Red sin privilegios (AV:N, PR:N, UI:N). Host confusion por canonicalización inconsistente permite bypass de políticas de validación y acceso a recursos no autorizados.

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 ScanningUser Account ManagementRestrict File and Directory PermissionsPrivileged Account ManagementRemote Data StorageNetwork Segmentation

Tecnologías afectadas (1)

Openjsf — Fast-uri

CWE

Referencias

JSON original (NVD)

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{
  "id": "CVE-2026-75931",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-75931",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-08-24T16:28:35.705177Z"
        }
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    "cvssMetricV31": [
      {
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        "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
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  "affected": [
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      "affectedData": [
        {
          "vendor": "fast-uri",
          "product": "fast-uri",
          "versions": [
            {
              "status": "affected",
              "version": "2.4.2",
              "lessThan": "2.4.5",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "2.4.5",
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            },
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              "status": "affected",
              "version": "3.1.3",
              "lessThan": "3.1.6",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "3.1.6",
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              "status": "unaffected",
              "version": "4.1.3",
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          "packageURL": "pkg:npm/fast-uri",
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  "published": "2026-08-24T10:16:40.113",
  "references": [
    {
      "url": "https://cna.openjsf.org/security-advisories.html",
      "tags": [
        "Vendor Advisory"
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      "source": "ce714d77-add3-4f53-aff5-83d477b104bb"
    },
    {
      "url": "https://github.com/fastify/fast-uri/security/advisories/GHSA-5jgf-p345-68v8",
      "tags": [
        "Vendor Advisory",
        "Mitigation"
      ],
      "source": "ce714d77-add3-4f53-aff5-83d477b104bb"
    }
  ],
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "ce714d77-add3-4f53-aff5-83d477b104bb",
      "description": [
        {
          "lang": "en",
          "value": "CWE-436"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "fast-uri is a URI parser for Node.js. It canonicalizes a host to its ASCII form only when the input carries an explicit scheme, so a scheme-relative reference such as a host preceded by two slashes is returned with its host verbatim and no error set. As a result fast-uri's own entry points disagree with each other: parse, resolve, normalize, and equal can yield different hosts for the same input depending only on whether a scheme is written out, and equal can return opposite verdicts for the same pair of hosts. An application that extracts a host with fast-uri to check it against a policy list and then resolves the same reference can make its decision on one host while the destination is another, enabling host confusion and policy bypass. The affected versions are 2.4.2 up to but not including 2.4.5, 3.1.3 up to but not including 3.1.6, and 4.0.1 up to but not including 4.1.3. The issue is fixed in 2.4.5, 3.1.6, and 4.1.3, which canonicalize the host consistently across the resolve path. Users should upgrade to a patched version."
    }
  ],
  "lastModified": "2026-09-02T14:44:52.047",
  "configurations": [
    {
      "nodes": [
        {
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          "operator": "OR"
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}