CVE-2026-6684

FatFs prior to R0.16 that use GPT scanning with 'FF_LBA64 = 1' contains an issue where an unbounded loop count derived from GPT header field GPTH_PtNum, enabling extremely long or effectively infinite mount-time scans. This maps to CWE-835 (Loop with Unreachable Exit Condition). Estimated CVSS v3.1 vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H (4.6, Medium). The estimated CISA SSVC vectors are Exploitation: PoC, Technical Impact: Partial.

CVSS 3.1

4.6CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

0.3% chance of exploitation in the next 30 days; higher than 23% of CVEs (scores of 2026-10-25)

CWE

CWE-835

Published

2026-07-01

Modified

2026-10-25

Record from

the NVD, synced 2026-10-25

Affected

• elm-chan:fatfs

References

• https://elm-chan.org/fsw/ff/
• https://github.com/runZeroInc/vulns-2026-fatfs-chance
• https://www.runzero.com/advisories/fatfs-gpt-scan-loop-dos-cve-2026-6684/
• https://www.runzero.com/blog/fatfs-bugs/
• https://github.com/runZeroInc/vulns-2026-fatfs-chance

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