CVE-2026-6688 FatFs Buffer Overflow via Unbounded LFN Filename Copy
Attackers can trigger buffer overflows in FatFs by providing long filenames, potentially leading to code execution or system crashes.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-6688?
CVE-2026-6688 is a high-severity memory corruption vulnerability in ChaN FatFs, published on 1 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
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.
Weakness: CWE-120
Which versions are affected by CVE-2026-6688?
It affects 1 product.
Products include Elm-Chan Fatfs.
How do I fix CVE-2026-6688?
No fix has been published for CVE-2026-6688 yet. Limit exposure of the affected software until one is available.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-6688 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-6688 exists.
Other vulnerabilities in ChaN FatFs
- CVE-2026-6682 FatFs Integer Overflow in FAT32 Volume Mount
- CVE-2026-6687 FatFs Stack Buffer Overflow via Uncapped exFAT Label Length
- CVE-2026-6683 FatFs Divide-by-Zero in exFAT Sync
- CVE-2026-6684 FatFs Infinite Loop in GPT Partition Scan
- CVE-2026-6686 FatFs Use of Uninitialized Clusters After Seek Past EOF
Sources
Also known as GHSA-8vm2-mjff-2gg2.