Cyber Resilience

CVE-2026-6682

Memory Safety in Elm-Chan Fatfs ≤ r0.16

Public PoCMemory Safety
Published
01 July 2026
Modified
02 July 2026
Patch / advisory
View advisory
CVSS Score v3.1 7.6
Click a component to see what it means
Raw vectorCVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
EPSS Score 0.0043 35th percentile
Risk Priority 55 floored blend · peak EPSS

Summary

CVE-2026-6682 is a high-severity Integer Overflow or Wraparound (CWE-190) vulnerability in Elm-Chan Fatfs. Its CVSS base score is 7.6 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); 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.

EU & UK References

Vulnerability Data

In FatFS R0.16 and earlier contains a FAT32 integer overflow bug in mount_volume() where fasize *= fs->n_fats can wrap, leading to attacker-controlled file-size metadata and unsafe read lengths in downstream callers. This maps to CWE-190 (Integer Overflow or Wraparound). Estimated…

more

CVSS v3.1 vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H (7.6, High). Remote delivery is also possible in OTA/update pipelines. The estimated CISA SSVC vectors are Exploitation: PoC, Technical Impact: Total.

CWE(s)
CWE-190

Related Threats

MITRE ATT&CK Enterprise TechniquesAI

T1068 Exploitation for Privilege Escalation Privilege Escalation
Adversaries may exploit software vulnerabilities in an attempt to elevate privileges.
attack.mitre.org →
T1203 Exploitation for Client Execution Execution
Adversaries may exploit software vulnerabilities in client applications to execute code.
attack.mitre.org →
Why these techniques?

Integer overflow in filesystem mount enables memory corruption leading to code execution or privilege escalation when attacker-controlled media or OTA images are processed.

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.

T1068 Exploitation for Privilege Escalation Privilege Escalationconfidence: HIGH
Integer overflow produces attacker-controlled metadata and unsafe read lengths that directly enable memory corruption leading to privilege escalation.
attack.mitre.org →
T1195 Supply Chain Compromise Initial Accessconfidence: MEDIUM
Vulnerability description explicitly notes remote delivery via OTA/update pipelines, facilitating supply-chain compromise of firmware images containing FAT volumes.
attack.mitre.org →
T1200 Hardware Additions Initial Accessconfidence: MEDIUM
Malicious FAT32 image can be delivered via physical media (SD/USB) that triggers the overflow on mount.
attack.mitre.org →
inferred from description + CWE · MITRE ATT&CK Enterprise v19.0

CVEs Like This One

CVE-2026-6687Same product: Elm-Chan Fatfs
CVE-2026-6688Same product: Elm-Chan Fatfs
CVE-2026-6684Same product: Elm-Chan Fatfs
CVE-2026-6683Same product: Elm-Chan Fatfs
CVE-2026-6686Same product: Elm-Chan Fatfs
CVE-2026-42199Shared CWE-190
CVE-2026-40449Shared CWE-190
CVE-2026-41664Shared CWE-190
CVE-2026-53910Shared CWE-190
CVE-2025-7709Shared CWE-190

Affected Assets

elm-chan
fatfs
≤ r0.16

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)
  • SI-2 Flaw Remediation
  • SI-10 Information Input Validation
  • SA-11 Developer Testing and Evaluation
Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)

—

Validate
Prove the fix (OWASP ASVS)
  • V5.2.6

Mitigating Controls (NIST 800-53 r5) AI

SI-2 Flaw Remediation good match
prevent

Directly requires timely patching or replacement of FatFS to eliminate the mount_volume integer overflow.

SI-10 Information Input Validation good match
prevent

Enforces validation of FAT32 metadata fields (fasize, n_fats) before arithmetic, blocking the wrap that produces attacker-controlled lengths.

SA-11 Developer Testing and Evaluation partial match
prevent

Requires developer testing and static analysis specifically for integer-overflow conditions in file-system mount paths.

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 require use of safe arithmetic, bounds checks, and testing that prevent integer overflows.

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 integer overflows before release.

A.8.25 Secure development life cycle partial match
prevents

Secure SDLC mandates input validation and arithmetic checks that prevent integer overflows.

A.8.26 Application security requirements partial match
degrades

Application security requirements include bounds checking and safe arithmetic to avoid overflow conditions.

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

Secure architecture principles require defensive coding patterns that mitigate integer wraparound risks.

A.8.28 Secure coding partial match
prevents

Secure coding standards explicitly forbid unsafe integer operations and mandate overflow-safe constructs.

References