CVE-2026-6686

{
  "id": "CVE-2026-6686",
  "sourceIdentifier": "44488dab-36db-4358-99f9-bc116477f914",
  "published": "2026-07-01T15:17:12.763",
  "lastModified": "2026-10-25T17:10:00.197",
  "vulnStatus": "Analyzed",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "FatFs R0.16 and earlier contains an uninitialized cluster exposure when f_lseek() extends files beyond EOF without zero-filling newly allocated clusters. This maps to CWE-908 (Use of Uninitialized Resource). Estimated CVSS v3.1 vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N (4.6, Medium). The estimated CISA SSVC vectors are Exploitation: PoC, Technical Impact: Partial."
    },
    {
      "lang": "es",
      "value": "FatFs R0.16 y anteriores contiene una exposición de clúster no inicializado cuando f_lseek() extiende archivos más allá del EOF sin rellenar con ceros los clústeres recién asignados. Esto se mapea a CWE-908 (Uso de Recurso No Inicializado). Vector CVSS v3.1 estimado: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N (4.6, Medio). Los vectores SSVC de CISA estimados son Explotación: PoC, Impacto Técnico: Parcial."
    }
  ],
  "affected": [
    {
      "source": "44488dab-36db-4358-99f9-bc116477f914",
      "affectedData": [
        {
          "vendor": "ChaN",
          "product": "FatFs",
          "defaultStatus": "unaffected",
          "versions": [
            {
              "version": "0",
              "lessThanOrEqual": "R0.16",
              "versionType": "custom",
              "status": "affected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {
    "cvssMetricV31": [
      {
        "source": "44488dab-36db-4358-99f9-bc116477f914",
        "type": "Secondary",
        "cvssData": {
          "version": "3.1",
          "vectorString": "CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N",
          "baseScore": 4.6,
          "baseSeverity": "MEDIUM",
          "attackVector": "PHYSICAL",
          "attackComplexity": "LOW",
          "privilegesRequired": "NONE",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "NONE",
          "availabilityImpact": "NONE"
        },
        "exploitabilityScore": 0.9,
        "impactScore": 3.6
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "timestamp": "2026-07-01T15:05:23.138301Z",
          "id": "CVE-2026-6686",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "version": "2.0.3"
        }
      }
    ]
  },
  "weaknesses": [
    {
      "source": "44488dab-36db-4358-99f9-bc116477f914",
      "type": "Secondary",
      "description": [
        {
          "lang": "en",
          "value": "CWE-908"
        }
      ]
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "operator": "OR",
          "negate": false,
          "cpeMatch": [
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:a:elm-chan:fatfs:*:*:*:*:*:*:*:*",
              "versionEndIncluding": "r0.16",
              "matchCriteriaId": "B99160BB-C4F5-4DA0-9FC9-0723E0633E00"
            }
          ]
        }
      ]
    }
  ],
  "references": [
    {
      "url": "https://elm-chan.org/fsw/ff/",
      "source": "44488dab-36db-4358-99f9-bc116477f914",
      "tags": [
        "Product"
      ]
    },
    {
      "url": "https://github.com/runZeroInc/vulns-2026-fatfs-chance",
      "source": "44488dab-36db-4358-99f9-bc116477f914",
      "tags": [
        "Third Party Advisory",
        "Exploit"
      ]
    },
    {
      "url": "https://www.runzero.com/advisories/fatfs-uninit-cluster-exposure-cve-2026-6686/",
      "source": "44488dab-36db-4358-99f9-bc116477f914",
      "tags": [
        "Third Party Advisory"
      ]
    },
    {
      "url": "https://www.runzero.com/blog/fatfs-bugs/",
      "source": "44488dab-36db-4358-99f9-bc116477f914",
      "tags": [
        "Third Party Advisory",
        "Exploit"
      ]
    },
    {
      "url": "https://github.com/runZeroInc/vulns-2026-fatfs-chance",
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "tags": [
        "Third Party Advisory",
        "Exploit"
      ]
    }
  ]
}