Cyber Resilience

CVE-2026-6684

DoS in Elm-Chan Fatfs ≤ r0.16

Public PoCDoS
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-2026-6684 is a medium-severity Infinite Loop (CWE-835) 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.

EU & UK References

Vulnerability Data

FatFs prior to R0.16 that use GPT scanning with 'FF_LBA64 = 1' contains an issue where an unbounded loop count derived from GPT header field GPTH_PtNum, enabling extremely long or effectively infinite mount-time scans. This maps to CWE-835 (Loop with…

more

Unreachable Exit Condition). 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). The estimated CISA SSVC vectors are Exploitation: PoC, Technical Impact: Partial.

CWE(s)
CWE-835

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?

Infinite loop in GPT mount parsing (CWE-835) directly enables application/system DoS via crafted removable media.

Confidence: HIGH · 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: HIGH
Unbounded loop from GPTH_PtNum during GPT mount directly enables application/system denial of service via crafted volume.
attack.mitre.org →
inferred from description + CWE · MITRE ATT&CK Enterprise v19.0

CVEs Like This One

CVE-2026-6683Same product: Elm-Chan Fatfs
CVE-2026-6687Same product: Elm-Chan Fatfs
CVE-2026-6688Same product: Elm-Chan Fatfs
CVE-2026-6682Same product: Elm-Chan Fatfs
CVE-2026-6686Same product: Elm-Chan Fatfs
CVE-2025-71330Shared CWE-835
CVE-2026-23082Shared CWE-835
CVE-2026-6521Shared CWE-835
CVE-2026-34852Shared CWE-835
CVE-2026-4179Shared CWE-835

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 enforces validation of GPT header fields such as GPTH_PtNum to bound loop iterations and reject malformed partition tables before mount.

SI-2 Flaw Remediation good match
prevent

Requires prompt application of the FatFs R0.16 patch that eliminates the unbounded loop derived from the GPT header.

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

Provides integrity verification of filesystem metadata on removable or external media prior to parsing, detecting tampering that triggers the infinite scan.

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 (reviews, testing, static analysis) directly prevent introduction of infinite-loop defects.

ID.RA-01 partial match
prevents

Static analysis and vuln scanning during asset assessment can detect unreachable loop exits.

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 can uncover infinite-loop conditions before release.

A.8.25 Secure development life cycle partial match
prevents

Secure development life cycle mandates practices that can detect and prevent infinite-loop defects.

A.8.26 Application security requirements partial match
prevents

Application security requirements can specify loop-termination rules, indirectly reducing the weakness.

A.8.28 Secure coding partial match
prevents

Secure coding standards directly address loop termination and prevent infinite loops.

A.8.27 Secure system architecture and engineering principles none match
none

Secure architecture principles encourage designs that avoid unreachable exit conditions.

A.8.32 Change management none match
none

Change management can require review of loop logic when code is modified.

References