CVE-2026-6687

HIGH 7.6

FatFs Stack Buffer Overflow via Uncapped exFAT Label Length

CVSS Score

7.6

EPSS Score

0.0%

EPSS Percentile

0th

FatFs R0.16 and earlier contains a stack overflow bug in f_getlabel() because exFAT label length (XDIR_NumLabel) is trusted without enforcing spec maximums. This maps to CWE-121 (Stack-based Buffer Overflow). Estimated CVSS v3.1 vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H (7.6, High). The estimated CISA SSVC vectors are Exploitation: PoC, Technical Impact: Total.

CWE	CWE-121
Vendor	chan
Product	fatfs
Published	Jul 1, 2026
Last Updated	Jul 1, 2026

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CVSS v3 Breakdown

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

Attack Vector

Physical

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Changed

Confidentiality

High

Integrity

High

Availability

High

Affected Versions

ChaN / FatFs

0 ≤ R0.16

References

NVD ↗ CVE.org ↗ EPSS Data ↗

runzero.com: https://www.runzero.com/blog/fatfs-bugs/ github.com: https://github.com/runZeroInc/vulns-2026-fatfs-chance elm-chan.org: https://elm-chan.org/fsw/ff/ runzero.com: https://www.runzero.com/advisories/fatfs-exfat-label-len-of-cve-2026-6687/

Credits

HD Moore of runZero, Inc. Tod Beardsley of runZero, Inc.