{"cve":"CVE-2026-6686","nvd":{"published":"2026-07-01T15:17:12.763","modified":"2026-10-25T17:10:00.197","status":"Analyzed","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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N","score":4.6},"cwes":["CWE-908"],"references":["https://elm-chan.org/fsw/ff/","https://github.com/runZeroInc/vulns-2026-fatfs-chance","https://www.runzero.com/advisories/fatfs-uninit-cluster-exposure-cve-2026-6686/","https://www.runzero.com/blog/fatfs-bugs/","https://github.com/runZeroInc/vulns-2026-fatfs-chance"],"products":["elm-chan:fatfs"],"source":"nvd","synced_at":"2026-10-25T17:50:06.907763985+00:00"},"epss":{"cve":"CVE-2026-6686","score":0.00255,"percentile":0.16923,"date":"2026-10-25"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}