CVE WatchJul 2, 2026

CVE-2026-6686

FatFs R0.16 and earlier contains an uninitialized cluster exposure when f_lseek() extends files beyond EOF without zero-filling newly alloca

CVSS

4.6

Medium

EPSS

0.2%

KEV

—

Exploit Today

0-100

Published: Jul 1, 2026 · Last modified: Jul 2, 2026 · CWE-908

EPSS · 30d

0.2%EPSS · 30 days0.2%

2026-07-022026-07-17

Technical 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.

Official references

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