Quick answers
- Is CVE-2026-6683 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-6683 being exploited in the wild.
- How severe is CVE-2026-6683?
- Medium severity, with a CVSS score of 4.6, published 1 July 2026.
- Which products and versions are affected?
- ChaN FatFs R0.16 and earlier.
- Is there a fix for CVE-2026-6683?
- No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
- How is CVE-2026-6683 attacked?
- It is attacked with physical access, in a software library.
- Am I affected by CVE-2026-6683?
- Check whether you run ChaN FatFs at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
A divide-by-zero vulnerability (CWE-369) exists in the exFAT free-space accounting logic within the sync_fs() function. When a crafted exFAT volume sets the BPB_NumClusEx field to zero, the internal variable n_fatent collapses to 2, resulting in a division by zero during arithmetic operations used to calculate cluster usage percentages. The vulnerability is triggered during f_write, f_sync, or f_close operations on the affected volume. This leads to a processor hard fault or SIGFPE, causing a denial of service. While primarily a physical attack vector via malicious media, it may be reachable remotely in systems that process network-delivered disk images or OTA updates.
Affected products
- ChaN FatFs R0.16 and earlier
Timeline
- 2026-07-01: disclosed: Vulnerability published in NVD and by runZero research team.