CVE-2026-6688

FatFs R0.16 and earlier contains a downstream-caller vulnerability pattern associated with FatFs long filename handling. With LFN enabled, fno.fname can be up to 255 characters; many callers copy it into short fixed buffers without bounds checks, causing overflow. This maps to CWE-120 (Buffer Copy without Checking Size of Input). Estimated 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). The estimated CISA SSVC vectors are Exploitation: PoC, Technical Impact: Total.

CVSS v3 7.6 HIGH

7.6^/10

CVSS v3 : HIGH

Vector :

Exploitability : 0.9 / Impact : 6.0

Attack Vector PHYSICAL

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact HIGH

Integrity Impact HIGH

Availability Impact HIGH

Scope CHANGED

References

Link	Resource
https://elm-chan.org/fsw/ff/	Product
https://github.com/runZeroInc/vulns-2026-fatfs-chance	Third Party Advisory Exploit
https://www.runzero.com/advisories/fatfs-long-fn-of-downstream-cve-2026-6688/	Third Party Advisory
https://www.runzero.com/blog/fatfs-bugs/	Third Party Advisory Exploit
https://github.com/runZeroInc/vulns-2026-fatfs-chance	Third Party Advisory Exploit

Configurations

Configuration 1 (hide)

cpe:2.3:a:elm-chan:fatfs:*:*:*:*:*:*:*:*

History

25 Oct 2026, 17:10

Type	Values Removed	Values Added
Summary		(es) FatFs R0.16 y anteriores contiene un patrón de vulnerabilidad de llamador descendente asociado con el manejo de nombres de archivo largos de FatFs. Con LFN habilitado, fno.fname puede tener hasta 255 caracteres; muchos llamadores lo copian en búferes fijos cortos sin comprobaciones de límites, causando desbordamiento. Esto corresponde a CWE-120 (Copia de búfer sin verificar el tamaño de la entrada). Vector CVSS v3.1 estimado: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H (7.6, Alta). Los vectores SSVC de CISA estimados son Explotación: PoC, Impacto técnico: Total.

Information

Published : 2026-07-01 15:17

Updated : 2026-10-25 17:10

NVD link : CVE-2026-6688

Mitre link : CVE-2026-6688

CVE.ORG link : CVE-2026-6688

JSON object : View

Products Affected

elm-chan

fatfs

CWE

CWE-120

Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')

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