CVE-2026-6687 PUBLISHED

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.

• HD Moore of runZero, Inc. finder
• Tod Beardsley of runZero, Inc. coordinator

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

• CWE-121 Stack-based buffer overflow CWE