CVE-2026-6686

Published: Jul 1, 2026Modified: Jul 2, 2026

4.6

Vector

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

Exploitability: 0.9 / Impact: 3.6

Source: 44488dab-36db-4358-99f9-bc116477f914 (Secondary)

Description

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: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N (4.6, Medium). The estimated CISA SSVC vectors are Exploitation: PoC, Technical Impact: Partial.

Affected (1)

Products: Elm Chan: Fatfs

1 product

Configuration A

1 vulnerable

Vulnerable Software	Affected Versions
Elm Chan Fatfs	Up to r0.16

Related CWEs

Use of Uninitialized Resource

The product uses or accesses a resource that has not been initialized.

References (5)

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

Source: 44488dab-36db-4358-99f9-bc116477f914

Product

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

Source: 44488dab-36db-4358-99f9-bc116477f914

Third Party AdvisoryExploit

https://www.runzero.com/advisories/fatfs-uninit-cluster-exposure-cve-2026-6686/

Source: 44488dab-36db-4358-99f9-bc116477f914

Third Party Advisory

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

Source: 44488dab-36db-4358-99f9-bc116477f914

Third Party AdvisoryExploit

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

Source: 134c704f-9b21-4f2e-91b3-4a467353bcc0

Third Party AdvisoryExploit

Timeline

No history available yet.