CVE-2026-6685

medium

Description

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). Estimated CVSS v3.1 vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H (6.1, Medium). The estimated CISA SSVC vectors are Exploitation: PoC, Technical Impact: Total.

References

https://www.runzero.com/blog/fatfs-bugs/

https://www.runzero.com/advisories/fatfs-unsigned-sub-wrap-cve-2026-6685/

https://github.com/runZeroInc/vulns-2026-fatfs-chance

https://elm-chan.org/fsw/ff/

Details

Source: Mitre, NVD

Published: 2026-07-01

Updated: 2026-07-01

Risk Information

CVSS v2

Base Score: 6.6

Vector: CVSS2#AV:L/AC:L/Au:N/C:N/I:C/A:C

Severity: Medium

CVSS v3

Base Score: 6.1

Vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

Severity: Medium