What is CVE-2026-6685?

CVE-2026-6685 is a medium-severity vulnerability in Chan Fatfs, classified under Integer Underflow. CVSS score: 6.1/10. Published 2026-07-01.

How severe is CVE-2026-6685?

Medium severity. CVSS v3 base score is 6.1 out of 10.

Integer overflow in Chan Fatfs

CVE-2026-6685

FatFs R0.16 and earlier exhibits a stale dirty-cache skip via unsigned-subtraction wrap in f_read() / f_write() (fp->sect - sect < cc) during interleaved read/write on fragmented filesystems. This maps to CWE-191 (Integer Underflow). Estim…

CVSS v3 metric

CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H.

Affected products

Chan Fatfs — versions 0

Weakness classification (CWE)

CWE-191 — Integer Underflow

References

44488dab-36db-4358-99f9-bc116477f914 (third-party-advisory)
44488dab-36db-4358-99f9-bc116477f914 (technical-description)
44488dab-36db-4358-99f9-bc116477f914 (product)
44488dab-36db-4358-99f9-bc116477f914 (third-party-advisory)

Frequently asked questions

What is CVE-2026-6685?: CVE-2026-6685 is a medium-severity vulnerability in Chan Fatfs, classified under Integer Underflow. CVSS score: 6.1/10. Published 2026-07-01.
How severe is CVE-2026-6685?: Medium severity. CVSS v3 base score is 6.1 out of 10.