CVE-2026-6683

FatFs Divide-by-Zero in exFAT Sync

CVSS 4.6 MEDIUMCWE-369

Vexday Risk Score

10Low

SSVC decision (CISA)

Track

No exploitation signal → monitor

CVSS 4.6EPSS —KEV nãoPoC —Nuclei —Metasploit —Patch —

Lifecycle

01 Jul 2026Published on NVD

Recommendation: Monitor — no exploitation signal at the moment.

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.

CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

ChaN · FatFs

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References

https://elm-chan.org/fsw/ff/https://github.com/runZeroInc/vulns-2026-fatfs-chance https://www.runzero.com/advisories/fatfs-exfat-divide-by-zero-cve-2026-6683 https://www.runzero.com/blog/fatfs-bugs/