CVE-2026-6683 FatFs Divide-by-Zero in exFAT Sync
Attackers can cause a denial of service in FatFs via crafted exFAT metadata triggering a divide-by-zero error during sync operations.
- 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-2026-6683?
CVE-2026-6683 is a medium-severity denial of service 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 divide-by-zero in exFAT sync logic bug when crafted metadata causes n_fatent - 2 to be zero during write/sync operations. This maps to CWE-369 (Divide By Zero). Estimated CVSS v3.1 vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H (4.6, Medium). Network-delivered update media can make this remote in some pipelines. The estimated CISA SSVC vectors are Exploitation: PoC, Technical Impact: Partial.
Weakness: CWE-369
Which versions are affected by CVE-2026-6683?
It affects 1 product.
Products include Elm-Chan Fatfs.
How do I fix CVE-2026-6683?
No fix has been published for CVE-2026-6683 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-6683 being exploited?
There is no known exploitation of CVE-2026-6683 in the wild and no public exploit code.
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-2026-6688 FatFs Buffer Overflow via Unbounded LFN Filename Copy
- 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-74cg-p8q3-4c3q.