CVE-2026-6686
FatFs Use of Uninitialized Clusters After Seek Past EOF
Vexday Risk Score
10Low
SSVC decision (CISA)
Track
No exploitation signal → monitor
CVSS 4.6EPSS —KEV nãoPoC —Nuclei —Metasploit —Patch —
Lifecycle
01 Jul 2026Published on NVD
Recommendation: Monitor — no exploitation signal at the moment.
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.
CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Affected products
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