{"id":"CVE-2026-6688","state":"PUBLISHED","title":"FatFs Buffer Overflow via Unbounded LFN Filename Copy","description":"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.","publishedAt":"2026-07-01T14:01:04.915Z","updatedAt":"2026-07-01T15:06:59.026Z","severity":{"score":7.6,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","source":"runZero"},"assigner":"runZero","products":["ChaN FatFs"],"affected":[{"vendor":"ChaN","product":"FatFs","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThanOrEqual":"R0.16","versionType":"custom"}]}],"references":["https://www.runzero.com/blog/fatfs-bugs/","https://github.com/runZeroInc/vulns-2026-fatfs-chance","https://elm-chan.org/fsw/ff/","https://www.runzero.com/advisories/fatfs-long-fn-of-downstream-cve-2026-6688/"],"weaknesses":["CWE-120"],"ingestedAt":"2026-10-29T20:12:49.727Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/6xxx/CVE-2026-6688.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-6688","state":"PUBLISHED","datePublished":"2026-07-01T14:01:04.915Z","dateUpdated":"2026-07-01T15:06:59.026Z","assignerShortName":"runZero","assignerOrgId":"44488dab-36db-4358-99f9-bc116477f914","dateReserved":"2026-04-20T15:06:24.308Z"},"containers":{"cna":{"title":"FatFs Buffer Overflow via Unbounded LFN Filename Copy","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."}],"affected":[{"vendor":"ChaN","product":"FatFs","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThanOrEqual":"R0.16","versionType":"custom"}]}],"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"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-120","lang":"en","description":"CWE-120 Buffer Copy without Checking Size of Input","type":"CWE"}]}],"providerMetadata":{"shortName":"runZero","orgId":"44488dab-36db-4358-99f9-bc116477f914","dateUpdated":"2026-07-01T14:01:44.487Z"},"datePublic":"2026-07-01T13:00:00.000Z","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":[{"title":"CISA ADP Vulnrichment","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"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-07-01T15:06:59.026Z"}}]}}}