{"id":"CVE-2026-6686","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-6686","generatedAt":"2026-10-28T07:03:57.987Z","title":"FatFs R0.16 and earlier contains an uninitialized cluster exposure when f_lseek() extends files beyond EOF without zero-filling newly allocated clusters.","description":"FatFs R0.16 and earlier contains an uninitialized cluster exposure when f_lseek() extends files beyond EOF without zero-filling newly allocated clusters. This maps to CWE-908 (Use of Uninitialized Resource). Estimated CVSS v3.1 vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N (4.6, Medium). The estimated CISA SSVC vectors are Exploitation: PoC, Technical Impact: Partial.","published":"2026-07-01T15:17:13.000Z","lastModified":"2026-10-25T17:10:00.000Z","status":"Analyzed","sourceIdentifier":"44488dab-36db-4358-99f9-bc116477f914","cvss":{"version":"3.1","score":4.6,"severity":"MEDIUM","vector":"CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N"},"cwe":["CWE-908"],"affected":["elm-chan/fatfs"],"epss":{"score":0.00255,"percentile":0.17,"date":"2026-10-27","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"low","text":"Lower severity and a low EPSS score (0.26%). Track it; it rarely justifies an emergency change on its own."},"changes":[],"references":[{"url":"https://elm-chan.org/fsw/ff/","tags":["Product"],"source":"44488dab-36db-4358-99f9-bc116477f914"},{"url":"https://github.com/runZeroInc/vulns-2026-fatfs-chance","tags":["Third Party Advisory","Exploit"],"source":"44488dab-36db-4358-99f9-bc116477f914"},{"url":"https://www.runzero.com/advisories/fatfs-uninit-cluster-exposure-cve-2026-6686/","tags":["Third Party Advisory"],"source":"44488dab-36db-4358-99f9-bc116477f914"},{"url":"https://www.runzero.com/blog/fatfs-bugs/","tags":["Third Party Advisory","Exploit"],"source":"44488dab-36db-4358-99f9-bc116477f914"},{"url":"https://github.com/runZeroInc/vulns-2026-fatfs-chance","tags":["Third Party Advisory","Exploit"],"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-6686","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}