What is CVE-2026-6686?

CVE-2026-6686 is a medium-severity vulnerability in Chan Fatfs, classified under Use of Uninitialized Resource. CVSS score: 4.6/10. Published 2026-07-01.

How severe is CVE-2026-6686?

Medium severity. CVSS v3 base score is 4.6 out of 10.

Vulnerability in Chan Fatfs

CVE-2026-6686

FatFs R0.16 and earlier contains an uninitialized cluster exposure when f_lseek() extends files beyond EOF without zero-filling newly allocated clusters. This maps to CWE-908 (Use of Uninitialized Resource). Estimated CVSS v3.1 vector: CVS…

CVSS v3 metric

CVSS v3 base score 4.6 (Medium). Vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.

Affected products

Chan Fatfs — versions 0

Weakness classification (CWE)

CWE-908 — Use of Uninitialized Resource

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-2026-6686?: CVE-2026-6686 is a medium-severity vulnerability in Chan Fatfs, classified under Use of Uninitialized Resource. CVSS score: 4.6/10. Published 2026-07-01.
How severe is CVE-2026-6686?: Medium severity. CVSS v3 base score is 4.6 out of 10.