PT-2026-54927 · Chan · Fatfs

Hd Moore + 2 · Published 2026-07-01 · Updated 2026-07-01 · CVE-2026-6685

Mitre

CVSS v3.1

6.1

Medium

Base vector

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

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.

Exploit

Fix

Integer Underflow

Weakness Enumeration

CWE-191

Related Identifiers

CVE-2026-6685

Affected Products

Fatfs

References · 5

• 🔥 https://github.com/runZeroInc/vulns-2026-fatfs-chance · Exploit
• https://nvd.nist.gov/vuln/detail/CVE-2026-6685 · Security Note
• https://runzero.com/advisories/fatfs-unsigned-sub-wrap-cve-2026-6685 · Note
• https://elm-chan.org/fsw/ff · Note
• https://runzero.com/blog/fatfs-bugs · Note