CVE-2026-6687
FatFs Stack Buffer Overflow via Uncapped exFAT Label Length
- State
- Published
- Severity
- 7.6 High
- Published
- Jul 1, 2026
- Updated
- Jul 1, 2026
- Reserved
- Apr 20, 2026
Description
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 3.1 | 7.6 High | CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H | runZero |
Weaknesses
- CWE-121 Stack-based buffer overflow
Affected Products
| Product | Versions |
|---|---|
FatFsChaN |
|
References
- https://www.runzero.com/blog/fatfs-bugs/third-party-advisory
- https://github.com/runZeroInc/vulns-2026-fatfs-chancetechnical-description
- https://elm-chan.org/fsw/ff/product
- https://www.runzero.com/advisories/fatfs-exfat-label-len-of-cve-2026-6687/third-party-advisory
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