CVE-2026-6682
In FatFS R0.16 and earlier contains a FAT32 integer overflow bug in mount_volume() where fasize *= fs->n_fats can wrap, leading to attacker-controlled file-size metadata and unsafe read lengths in downstream callers.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.32%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
In FatFS R0.16 and earlier contains a FAT32 integer overflow bug in mount_volume() where fasize *= fs->n_fats can wrap, leading to attacker-controlled file-size metadata and unsafe read lengths in downstream callers. This maps to CWE-190 (Integer Overflow or Wraparound). 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). Remote delivery is also possible in OTA/update pipelines. 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
- 0.32% probability · 25th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-190
- Affected
- elm-chan/fatfs
- Source
- 44488dab-36db-4358-99f9-bc116477f914
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-fat32-int-of-mnt-cve-2026-6682/Third Party Advisory, Exploit
- 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. Refreshed daily.