Buffer overflow in Chan Fatfs
CVE-2026-6688
FatFs R0.16 and earlier contains a downstream-caller vulnerability pattern associated with FatFs long filename handling. With LFN enabled, fno.fname can be up to 255 characters; many callers copy it into short fixed buffers without bounds checks, causing overflow. This maps to CWE-120 (Buffer Copy without Checking Size of Input). 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.
Vulnerability class: Buffer Overflow
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.6 (High). Vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.003 (22.9th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 23rd percentile — 22.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: 0.000
Affected products
- Chan Fatfs — versions 0
- Elm-Chan Fatfs
Weakness classification (CWE)
References
- 44488dab-36db-4358-99f9-bc116477f914 (Exploit, Third Party Advisory, third-party-advisory)
- 44488dab-36db-4358-99f9-bc116477f914 (Exploit, technical-description, Third Party Advisory)
- 44488dab-36db-4358-99f9-bc116477f914 (Product, product)
- 44488dab-36db-4358-99f9-bc116477f914 (Third Party Advisory, third-party-advisory)
Frequently asked questions
- What is CVE-2026-6688?
- CVE-2026-6688 is a high-severity vulnerability in Chan Fatfs, classified under Buffer Copy without Checking Size of Input (Classic Buffer Overflow). CVSS score: 7.6/10. Published 2026-07-01.
- How severe is CVE-2026-6688?
- High severity. CVSS v3 base score is 7.6 out of 10.