FKIE_CVE-2026-6685

Vulnerability from fkie_nvd - Published: 2026-07-01 15:17 - Updated: 2026-07-01 18:31
Severity
6.1 (Medium) - CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
Summary
FatFs R0.16 and earlier exhibits a stale dirty-cache skip via unsigned-subtraction wrap in f_read() / f_write() (fp->sect - sect < cc) during interleaved read/write on fragmented filesystems. This maps to CWE-191 (Integer Underflow). Estimated CVSS v3.1 vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H (6.1, Medium). The estimated CISA SSVC vectors are Exploitation: PoC, Technical Impact: Total.
References
44488dab-36db-4358-99f9-bc116477f914https://elm-chan.org/fsw/ff/
44488dab-36db-4358-99f9-bc116477f914https://github.com/runZeroInc/vulns-2026-fatfs-chance
44488dab-36db-4358-99f9-bc116477f914https://www.runzero.com/advisories/fatfs-unsigned-sub-wrap-cve-2026-6685/
44488dab-36db-4358-99f9-bc116477f914https://www.runzero.com/blog/fatfs-bugs/
134c704f-9b21-4f2e-91b3-4a467353bcc0https://github.com/runZeroInc/vulns-2026-fatfs-chance
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "FatFs",
          "vendor": "ChaN",
          "versions": [
            {
              "lessThanOrEqual": "R0.16",
              "status": "affected",
              "version": "0",
              "versionType": "custom"
            }
          ]
        }
      ],
      "source": "44488dab-36db-4358-99f9-bc116477f914"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "FatFs R0.16 and earlier exhibits a stale dirty-cache skip via unsigned-subtraction wrap in f_read() / f_write() (fp-\u003esect - sect \u003c cc) during interleaved read/write on fragmented filesystems. This maps to CWE-191 (Integer Underflow). Estimated CVSS v3.1 vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H (6.1, Medium). The estimated CISA SSVC vectors are Exploitation: PoC, Technical Impact: Total."
    }
  ],
  "id": "CVE-2026-6685",
  "lastModified": "2026-07-01T18:31:17.080",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "PHYSICAL",
          "availabilityImpact": "HIGH",
          "baseScore": 6.1,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "NONE",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 0.9,
        "impactScore": 5.2,
        "source": "44488dab-36db-4358-99f9-bc116477f914",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-6685",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-07-01T15:26:17.001634Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-07-01T15:17:12.660",
  "references": [
    {
      "source": "44488dab-36db-4358-99f9-bc116477f914",
      "url": "https://elm-chan.org/fsw/ff/"
    },
    {
      "source": "44488dab-36db-4358-99f9-bc116477f914",
      "url": "https://github.com/runZeroInc/vulns-2026-fatfs-chance"
    },
    {
      "source": "44488dab-36db-4358-99f9-bc116477f914",
      "url": "https://www.runzero.com/advisories/fatfs-unsigned-sub-wrap-cve-2026-6685/"
    },
    {
      "source": "44488dab-36db-4358-99f9-bc116477f914",
      "url": "https://www.runzero.com/blog/fatfs-bugs/"
    },
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "url": "https://github.com/runZeroInc/vulns-2026-fatfs-chance"
    }
  ],
  "sourceIdentifier": "44488dab-36db-4358-99f9-bc116477f914",
  "vulnStatus": "Undergoing Analysis",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-191"
        }
      ],
      "source": "44488dab-36db-4358-99f9-bc116477f914",
      "type": "Secondary"
    }
  ]
}


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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
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Detection rules are retrieved from Rulezet.