CVE-2026-6686

FatFs Use of Uninitialized Clusters After Seek Past EOF

Published Jul 1, 2026 CVSS 3.1 · 4.6 Medium EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
First Time appeared Chan
Chan fatfs
Vendors & Products Chan
Chan fatfs
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
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.
Title FatFs Use of Uninitialized Clusters After Seek Past EOF
Weaknesses CWE-908
References
Metrics cvssV3_1

{'score': 4.6, 'vector': 'CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
runZero
Published
Updated
Jul 1, 2026, 3:05 PM
Reserved
Apr 20, 2026, 3:06 PM
Status
Analyzed
Published
Jul 1, 2026, 3:17 PM
Modified
Oct 25, 2026, 5:10 PM