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.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| ChaN | FatFs | ≤ R0.16 | — |
References
- https://www.runzero.com/blog/fatfs-bugs/ third-party-advisory
- https://github.com/runZeroInc/vulns-2026-fatfs-chance technical-description
- https://elm-chan.org/fsw/ff/ product
- https://www.runzero.com/advisories/fatfs-exfat-divide-by-zero-cve-2026-6683 third-party-advisory