CVE-2026-6688CWE-120

FatFs Buffer Overflow via Unbounded LFN Filename Copy

High · published July 1, 2026

CVSS v3.1
7.6
EPSS
0%
Percentile
24.0
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
7.6 · HIGH
Vector
CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
CVSS v4.0
Not supplied
EPSS
0.00322 · 24.0th percentile
Weakness
CWE-120 · Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
Published
2026-07-01T14:01Z
EPSS history
Timeline
  • 01 JUL 14:01Z
    FatFs Buffer Overflow via Unbounded LFN Filename Copy
    cvelistv5