Cyber Resilience

CVE-2026-6683

Elm-Chan Fatfs ≤ r0.16

Public PoC
Published
01 July 2026
Modified
02 July 2026
Patch / advisory
View advisory
CVSS Score v3.1 4.6
Click a component to see what it means
Raw vectorCVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS Score 0.0043 35th percentile
Risk Priority 35 floored blend · peak EPSS

Summary

CVE-2026-6683 is a medium-severity Divide By Zero (CWE-369) vulnerability in Elm-Chan Fatfs. Its CVSS base score is 4.6 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Application or System Exploitation (T1499.004); ranked at the 35th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.

The strongest mitigations our analysis identified map to SI-10 (Information Input Validation) and SI-2 (Flaw Remediation) — see the control section below for these in your framework.

OWASP Top 10 for Web (2025)

A10:2025 Mishandling of Exceptional Conditions

EU & UK References

Vulnerability Data

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…

more

update media can make this remote in some pipelines. The estimated CISA SSVC vectors are Exploitation: PoC, Technical Impact: Partial.

CWE(s)
CWE-369

Related Threats

MITRE ATT&CK Enterprise TechniquesAI

T1499.004 Application or System Exploitation Impact
Adversaries may exploit software vulnerabilities that can cause an application or system to crash and deny availability to users.
attack.mitre.org →
Why these techniques?

Divide-by-zero in filesystem metadata handling directly enables application/system DoS via crafted exFAT content (T1499.004).

Confidence: MEDIUM · MITRE ATT&CK Enterprise v19.0

Likely ATT&CK TechniquesAI

Techniques this vulnerability likely enables, inferred from its description, weakness type, and attributed-actor tradecraft. Confidence is per-technique.

T1499.004 Application or System Exploitation Impactconfidence: MEDIUM
Crafted exFAT metadata triggers divide-by-zero crash on access/sync, enabling application/system DoS via exploitation.
attack.mitre.org →
inferred from description + CWE · MITRE ATT&CK Enterprise v19.0

CVEs Like This One

CVE-2026-6684Same product: Elm-Chan Fatfs
CVE-2026-6687Same product: Elm-Chan Fatfs
CVE-2026-6682Same product: Elm-Chan Fatfs
CVE-2026-6688Same product: Elm-Chan Fatfs
CVE-2026-6686Same product: Elm-Chan Fatfs
CVE-2026-10679Shared CWE-369
CVE-2026-46184Shared CWE-369
CVE-2026-46161Shared CWE-369
CVE-2026-25169Shared CWE-369
CVE-2026-21996Shared CWE-369

Affected Assets

elm-chan
fatfs
≤ r0.16

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)
  • SI-10 Information Input Validation
  • SI-2 Flaw Remediation
Detect
Catch it (NIST detect / respond)
  • SI-7 Software, Firmware, and Information Integrity
Harden
Shrink the surface (DISA STIG)

—

Validate
Prove the fix (OWASP ASVS)

—

Mitigating Controls (NIST 800-53 r5) AI

SI-10 Information Input Validation good match
prevent

Directly validates exFAT metadata structures before FatFs sync/write operations, blocking the crafted n_fatent values that trigger the divide-by-zero.

SI-2 Flaw Remediation good match
prevent

Requires prompt application of patches that correct the exFAT sync logic flaw in FatFs R0.16 and earlier.

SI-7 Software, Firmware, and Information Integrity partial match
detect

Verifies integrity of filesystem metadata and update media, enabling detection of malformed exFAT content before it reaches vulnerable parsing code.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

Secure SDLC practices directly include code analysis, input validation, and testing that prevent divide-by-zero errors.

ID.RA-01 partial match
prevents

Vulnerability identification processes can discover divide-by-zero flaws via static analysis or testing.

PR.PS-02 partial match
prevents

Routine patching and replacement can remediate divide-by-zero bugs present in deployed software.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.29 Security testing in development and acceptance mostly match
detects

Security testing in development can detect divide-by-zero conditions before release.

A.8.25 Secure development life cycle partial match
prevents

Secure development lifecycle includes input validation and error-handling practices that can prevent divide-by-zero faults.

A.8.26 Application security requirements partial match
prevents

Application security requirements can mandate checks for zero denominators and safe arithmetic handling.

A.8.27 Secure system architecture and engineering principles partial match
prevents

Secure architecture principles encourage defensive coding patterns that avoid arithmetic exceptions.

A.8.28 Secure coding partial match
prevents

Secure coding standards directly require validation to prevent divide-by-zero and similar runtime faults.

References