CVE-2026-6683: Elm-Chan Fatfs

Medium severity, CVSS 4.6. EPSS: 0.3% chance of exploitation in the next 30 days.

FatFs R0.16 and earlier contains a divide-by-zero in exFAT sync logic bug when crafted metadata causes n_fatent - 2 to be zero during write/sync operations. This maps to CWE-369 (Divide By Zero). Estimated CVSS v3.1 vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H (4.6, Medium). Network-delivered update media can make this remote in some pipelines. The estimated CISA SSVC vectors are Exploitation: PoC, Technical Impact: Partial.

Affected products

• Elm-Chan Fatfs: up to and including r0.16

Published 2026-07-01. Last modified 2026-07-02.