Vulnerability-Lookup

CVE-2026-6688 (GCVE-0-2026-6688)

Vulnerability from cvelistv5 – Published: 2026-07-01 14:01 – Updated: 2026-07-01 15:06

Title

FatFs Buffer Overflow via Unbounded LFN Filename Copy

Summary

FatFs R0.16 and earlier contains a downstream-caller vulnerability pattern associated with FatFs long filename handling. With LFN enabled, fno.fname can be up to 255 characters; many callers copy it into short fixed buffers without bounds checks, causing overflow. This maps to CWE-120 (Buffer Copy without Checking Size of Input). Estimated CVSS v3.1 vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H (7.6, High). The estimated CISA SSVC vectors are Exploitation: PoC, Technical Impact: Total.

Severity

7.6 (High)


                        
                          CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

SSVC

Exploitation: poc Automatable: no Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-07-01 15:06 UTC

CWE

CWE-120 - Buffer Copy without Checking Size of Input

Assigner

runZero CNA under the icscert root

CNA scorecard C 71/100 over 31 records in the last 180 days details

References

4 references

URL	Tags
https://www.runzero.com/blog/fatfs-bugs/	third-party-advisory
https://github.com/runZeroInc/vulns-2026-fatfs-chance	technical-description
https://elm-chan.org/fsw/ff/	product
https://www.runzero.com/advisories/fatfs-long-fn-…	third-party-advisory

Impacted products

1 product

Vendor	Product	Version	CPE status
ChaN	FatFs	Affected: 0 , ≤ R0.16 (custom)	guessed

Date Public

2026-07-01 13:00

Credits

HD Moore of runZero, Inc. Tod Beardsley of runZero, Inc.

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-6688

Vulnerability from fkie_nvd - Published: 2026-07-01 15:17 - Updated: 2026-10-25 17:10

Severity

7.6 (High) - CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

Summary

References

URL	Tags
44488dab-36db-4358-99f9-bc116477f914	https://elm-chan.org/fsw/ff/	Product
44488dab-36db-4358-99f9-bc116477f914	https://github.com/runZeroInc/vulns-2026-fatfs-chance	Third Party Advisory, Exploit
44488dab-36db-4358-99f9-bc116477f914	https://www.runzero.com/advisories/fatfs-long-fn-of-downstream-cve-2026-6688/	Third Party Advisory
44488dab-36db-4358-99f9-bc116477f914	https://www.runzero.com/blog/fatfs-bugs/	Third Party Advisory, Exploit
134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/runZeroInc/vulns-2026-fatfs-chance	Third Party Advisory, Exploit

Impacted products

	Vendor	Product	Version
	elm-chan	fatfs	*

JSON

To clipboard

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          "id": "CVE-2026-6688",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-07-01T15:06:55.618764Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-07-01T15:17:13.013",
  "references": [
    {
      "source": "44488dab-36db-4358-99f9-bc116477f914",
      "tags": [
        "Product"
      ],
      "url": "https://elm-chan.org/fsw/ff/"
    },
    {
      "source": "44488dab-36db-4358-99f9-bc116477f914",
      "tags": [
        "Third Party Advisory",
        "Exploit"
      ],
      "url": "https://github.com/runZeroInc/vulns-2026-fatfs-chance"
    },
    {
      "source": "44488dab-36db-4358-99f9-bc116477f914",
      "tags": [
        "Third Party Advisory"
      ],
      "url": "https://www.runzero.com/advisories/fatfs-long-fn-of-downstream-cve-2026-6688/"
    },
    {
      "source": "44488dab-36db-4358-99f9-bc116477f914",
      "tags": [
        "Third Party Advisory",
        "Exploit"
      ],
      "url": "https://www.runzero.com/blog/fatfs-bugs/"
    },
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "tags": [
        "Third Party Advisory",
        "Exploit"
      ],
      "url": "https://github.com/runZeroInc/vulns-2026-fatfs-chance"
    }
  ],
  "sourceIdentifier": "44488dab-36db-4358-99f9-bc116477f914",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-120"
        }
      ],
      "source": "44488dab-36db-4358-99f9-bc116477f914",
      "type": "Secondary"
    }
  ]
}

GHSA-8VM2-MJFF-2GG2

Vulnerability from github – Published: 2026-07-01 15:35 – Updated: 2026-07-01 15:35

Details

Severity

7.6 (High)


                  
                    CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

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{
  "affected": [],
  "aliases": [
    "CVE-2026-6688"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-120"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-07-01T15:17:13Z",
    "severity": "HIGH"
  },
  "details": "FatFs R0.16 and earlier contains a downstream-caller vulnerability pattern associated with FatFs long filename handling. With LFN enabled, fno.fname can be up to 255 characters; many callers copy it into short fixed buffers without bounds checks, causing overflow. This maps to CWE-120 (Buffer Copy without Checking Size of Input). Estimated CVSS v3.1 vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H (7.6, High). The estimated CISA SSVC vectors are Exploitation: PoC, Technical Impact: Total.",
  "id": "GHSA-8vm2-mjff-2gg2",
  "modified": "2026-07-01T15:35:21Z",
  "published": "2026-07-01T15:35:21Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-6688"
    },
    {
      "type": "WEB",
      "url": "https://elm-chan.org/fsw/ff"
    },
    {
      "type": "WEB",
      "url": "https://github.com/runZeroInc/vulns-2026-fatfs-chance"
    },
    {
      "type": "WEB",
      "url": "https://www.runzero.com/advisories/fatfs-long-fn-of-downstream-cve-2026-6688"
    },
    {
      "type": "WEB",
      "url": "https://www.runzero.com/blog/fatfs-bugs"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}

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CVE-2026-6688 (GCVE-0-2026-6688)

FKIE_CVE-2026-6688

GHSA-8VM2-MJFF-2GG2

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