CVE-2026-6683
MediumCVSS 4.6Exploitation Probability (EPSS)
Low risk8th percentile - higher than 8% of all known CVEs
Summary
FatFs R0.16 and earlier contains a divide-by-zero bug in exFAT sync logic. Crafted metadata can cause n_fatent - 2 to be zero during write/sync operations, leading to a system crash.
Risk Assessment
An attacker with physical access can cause a denial of service (DoS). In network-delivered update scenarios, the attack can be remote, increasing risk for embedded and IoT systems.
Recommendation
Update FatFs to a version newer than R0.16 that fixes this bug. Restrict access to data media and monitor write/sync operations in critical systems.
Other vulnerabilities in FatFs
See all- CVE-2026-6688High
A vulnerability in FatFs R0.16 and earlier affects long filename (LFN) handling. The function copies filenames (up to 255 characters) into short fixed buffers without bounds checking, causing buffer overflow.
- CVE-2026-6687High
FatFs R0.16 and earlier contains a stack overflow bug in f_getlabel() because exFAT label length (XDIR_NumLabel) is trusted without enforcing spec maximums.
- CVE-2026-6686Medium
FatFs R0.16 and earlier contains an uninitialized cluster exposure when f_lseek() extends files beyond EOF without zero-filling newly allocated clusters. This can lead to data disclosure.
- CVE-2026-6684Medium
A vulnerability in FatFs prior to R0.16, using GPT scanning with 'FF_LBA64 = 1', causes an infinite loop during filesystem mounting. The issue stems from an unbounded loop count derived from the GPTH_PtNum field in the GPT header, leading to extremely long or infinite mount times.
- CVE-2026-6682High
In FatFS R0.16 and earlier, there is an 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.
Original NVD description (English source)
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.