Description
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.
References (4)
Core 4
Core References
Third Party Advisory third-party-advisory
https://www.runzero.com/blog/fatfs-bugs/
Technical Description technical-description
https://github.com/runZeroInc/vulns-2026-fatfs-chance
Product product
https://elm-chan.org/fsw/ff/
Third Party Advisory third-party-advisory
https://www.runzero.com/advisories/fatfs-exfat-divide-by-zero-cve-2026-6683
Scores
CVSS v3
4.6
EPSS
0.0043
EPSS Percentile
35.3%
Attack Vector
PHYSICAL
CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CISA SSVC
Vulnrichment
Exploitation
none
Automatable
no
Technical Impact
partial
Lab Environment
Details
CWE
CWE-369
Status
published
Products (2)
ChaN/FatFs
< R0.16
elm-chan/fatfs
< r0.16
Published
Jul 01, 2026
Tracked Since
Jul 01, 2026