CVE-2026-6682: Elm-Chan Fatfs

High severity, CVSS 7.6. EPSS: 0.3% chance of exploitation in the next 30 days.

In FatFS R0.16 and earlier contains a FAT32 integer overflow bug in mount_volume() where fasize *= fs->n_fats can wrap, leading to attacker-controlled file-size metadata and unsafe read lengths in downstream callers. This maps to CWE-190 (Integer Overflow or Wraparound). 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). Remote delivery is also possible in OTA/update pipelines. The estimated CISA SSVC vectors are Exploitation: PoC, Technical Impact: Total.

Affected products

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

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