What’s Vulnerable › Vulnerabilities

CVE-2026-6683: FatFs Divide-by-Zero in exFAT Sync

• Severity: medium (CVSS 4.6 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-07-01 · updated 2026-10-25
• Weakness: CWE-369

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

• ChaN FatFs: through r0.16

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/
• https://github.com/runZeroInc/vulns-2026-fatfs-chance

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