{"id":"CVE-2026-6688","aliases":["EUVD-2026-41000","GHSA-8vm2-mjff-2gg2"],"status":"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.","severity":{"version":"3.1","score":7.6,"vector":"CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-10","score":0.00322,"percentile":0.25476,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-120"],"published":"2026-07-01T14:01:04Z","modified":"2026-10-25T17:10:00Z","products":[{"vendor":"chan","product":"fatfs"},{"vendor":"elm-chan","product":"fatfs"}],"references":[{"url":"https://www.runzero.com/blog/fatfs-bugs/","tags":["third-party-advisory","Third Party Advisory","Exploit"]},{"url":"https://github.com/runZeroInc/vulns-2026-fatfs-chance","tags":["technical-description","exploit","Third Party Advisory","Exploit"]},{"url":"https://elm-chan.org/fsw/ff/","tags":["product","Product"]},{"url":"https://www.runzero.com/advisories/fatfs-long-fn-of-downstream-cve-2026-6688/","tags":["third-party-advisory","Third Party Advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-6688"},{"url":"https://elm-chan.org/fsw/ff"},{"url":"https://www.runzero.com/advisories/fatfs-long-fn-of-downstream-cve-2026-6688"},{"url":"https://www.runzero.com/blog/fatfs-bugs"},{"url":"https://github.com/advisories/GHSA-8vm2-mjff-2gg2"}],"sources":{"cve":[{"id":"CVE-2026-6688","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.","status":"published","published":"2026-07-01T14:01:04.915Z","modified":"2026-07-01T15:06:59.026Z","cvss":[{"version":"3.1","score":7.6,"vector":"CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","level":"high","assessor":"cna"}],"cwes":["CWE-120"],"updated_at":"2026-11-02T13:49:53.818886Z"}],"euvd":[{"id":"EUVD-2026-41000","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.","status":"published","published":"2026-07-01T14:01:04Z","modified":"2026-07-01T15:06:59Z","cvss":[{"version":"3.1","score":7.6,"vector":"CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","level":"high"}],"updated_at":"2026-11-02T18:20:19.829772Z"}],"ghsa":[{"id":"GHSA-8vm2-mjff-2gg2","title":"FatFs R0.16 and earlier contains a downstream-caller vulnerability pattern associated with FatFs...","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.","status":"published","published":"2026-07-01T15:35:21Z","modified":"2026-07-01T15:35:28Z","cvss":[{"version":"3.1","score":7.6,"vector":"CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","level":"high"}],"cwes":["CWE-120"],"updated_at":"2026-11-02T15:09:08.409779Z"}],"nvd":[{"id":"CVE-2026-6688","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.","status":"published","published":"2026-07-01T15:17:13.013Z","modified":"2026-10-25T17:10:00.197Z","cvss":[{"version":"3.1","score":7.6,"vector":"CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","level":"high","assessor":"secondary"}],"cwes":["CWE-120"],"updated_at":"2026-11-02T14:12:27.199837Z"}]}}