FatFs Divide-by-Zero in exFAT Sync

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Summary

CVECVE-2026-6683
StatePUBLISHED
AssignerrunZero
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-01 15:17:12 UTC
Updated2026-07-01 18:31:17 UTC
DescriptionFatFs 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.

Risk And Classification

Primary CVSS: v3.1 4.6 MEDIUM from 44488dab-36db-4358-99f9-bc116477f914

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

Problem Types: CWE-369 | CWE-369 CWE-369 Divide by zero

VersionSourceTypeScoreSeverityVector
3.144488dab-36db-4358-99f9-bc116477f914Secondary4.6MEDIUMCVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.1CNACVSS4.6MEDIUMCVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Physical
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA ChaN FatFs affected R0.16 custom Not specified

References

ReferenceSourceLinkTags
www.runzero.com/blog/fatfs-bugs 44488dab-36db-4358-99f9-bc116477f914 www.runzero.com
github.com/runZeroInc/vulns-2026-fatfs-chance 134c704f-9b21-4f2e-91b3-4a467353bcc0 github.com
www.runzero.com/advisories/fatfs-exfat-divide-by-zero-cve-2026-6683 44488dab-36db-4358-99f9-bc116477f914 www.runzero.com
elm-chan.org/fsw/ff 44488dab-36db-4358-99f9-bc116477f914 elm-chan.org
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: HD Moore of runZero, Inc. (en)

CNA: Tod Beardsley of runZero, Inc. (en)

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