{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-6688","assignerOrgId":"44488dab-36db-4358-99f9-bc116477f914","state":"PUBLISHED","assignerShortName":"runZero","dateReserved":"2026-04-20T15:06:24.308Z","datePublished":"2026-07-01T14:01:04.915Z","dateUpdated":"2026-07-01T15:06:59.026Z"},"containers":{"cna":{"providerMetadata":{"orgId":"44488dab-36db-4358-99f9-bc116477f914","shortName":"runZero","dateUpdated":"2026-07-01T14:01:44.487Z"},"title":"FatFs Buffer Overflow via Unbounded LFN Filename Copy","datePublic":"2026-07-01T13:00:00.000Z","problemTypes":[{"descriptions":[{"lang":"en","cweId":"CWE-120","description":"CWE-120 Buffer Copy without Checking Size of Input","type":"CWE"}]}],"affected":[{"vendor":"ChaN","product":"FatFs","versions":[{"status":"affected","version":"0","lessThanOrEqual":"R0.16","versionType":"custom"}],"defaultStatus":"unaffected"}],"descriptions":[{"lang":"en","value":"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.","supportingMedia":[{"type":"text/html","base64":false,"value":"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."}]}],"references":[{"url":"https://www.runzero.com/blog/fatfs-bugs/","tags":["third-party-advisory"]},{"url":"https://github.com/runZeroInc/vulns-2026-fatfs-chance","tags":["technical-description"]},{"url":"https://elm-chan.org/fsw/ff/","tags":["product"]},{"url":"https://www.runzero.com/advisories/fatfs-long-fn-of-downstream-cve-2026-6688/","tags":["third-party-advisory"]}],"metrics":[{"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}],"cvssV3_1":{"version":"3.1","attackVector":"PHYSICAL","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"CHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH","baseSeverity":"HIGH","baseScore":7.6,"vectorString":"CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H"}}],"credits":[{"lang":"en","value":"HD Moore of runZero, Inc.","type":"finder"},{"lang":"en","value":"Tod Beardsley of runZero, Inc.","type":"coordinator"}],"source":{"discovery":"UNKNOWN"},"x_generator":{"engine":"Vulnogram 1.0.2"}},"adp":[{"references":[{"url":"https://github.com/runZeroInc/vulns-2026-fatfs-chance","tags":["exploit"]}],"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-07-01T15:06:55.618764Z","id":"CVE-2026-6688","options":[{"Exploitation":"poc"},{"Automatable":"no"},{"Technical Impact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"title":"CISA ADP Vulnrichment","providerMetadata":{"orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","shortName":"CISA-ADP","dateUpdated":"2026-07-01T15:06:59.026Z"}}]}}