CVE-2026-6685 | FatFs R0.16 and earlier exhibits a stale dirty-cache skip vi… | CVSS 6.1 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.

Metadata

CVE ID: CVE-2026-6685
State: PUBLISHED
Assigner: runZero
Reserved: 2026-04-20 15:06 UTC
Published: 2026-07-01 13:47 UTC
Last updated: 2026-07-01 15:26 UTC
Primary CWE: CWE-191
CWE-191 Integer underflow (wrap or wraparound)
Vendor / Product: ChaN / FatFs
Sources: cve.org · NVD

Severity & Metrics

6.1 MEDIUM CVSS 3.1

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

SSVC — CISA Coordinator

Exploitation: PoC
Automatable: no
Tech. Impact: partial

Affected products (1)

Vendor	Product	Platform	Versions
ChaN	FatFs	—	0 ≤ R0.16

Weakness (CWE)

CWE	Source	Description
CWE-191	cna	CWE-191 Integer underflow (wrap or wraparound)

CVSS scores (1)

Score	Severity	Version	Source	Vector
6.1	MEDIUM	3.1	cna	CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

References (4)