CVE-2026-6687
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.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.35%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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.
- CVSS 3.1
- 7.6 HIGHCVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
- EPSS
- 0.35% probability · 28th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-121
- Affected
- elm-chan/fatfs
- Source
- 44488dab-36db-4358-99f9-bc116477f914
EPSS 0.3% since 27 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- https://elm-chan.org/fsw/ff/Product
- https://github.com/runZeroInc/vulns-2026-fatfs-chanceThird Party Advisory, Exploit
- https://www.runzero.com/advisories/fatfs-exfat-label-len-of-cve-2026-6687/Third Party Advisory
- https://www.runzero.com/blog/fatfs-bugs/Third Party Advisory, Exploit
- https://github.com/runZeroInc/vulns-2026-fatfs-chanceThird Party Advisory, Exploit
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.