How severe is CVE-2026-6688?

CVE-2026-6688 has a CVSS 3.x base score of 7.6, rated high severity. It is exploitable over physical access with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-6688 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (11th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-6688?

CVE-2026-6688 affects Elm-chan Fatfs. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-6688?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2026-6688 published?

CVE-2026-6688 was published on 2026-07-01 and last updated on 2026-07-02.

CVE-2026-6688

CVE-2026-6688 is a high-severity vulnerability in Elm-chan Fatfs with a CVSS 3.x base score of 7.6. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-120.

Key facts

Severity: High (CVSS 3.x base score 7.6)
EPSS exploit prediction: 0% (11th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-120
Affected product: Elm-chan Fatfs
Published: 2026-07-01
Last modified: 2026-07-02

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.

Frequently asked questions

What is 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.
How severe is CVE-2026-6688?: CVE-2026-6688 has a CVSS 3.x base score of 7.6, rated high severity. It is exploitable over physical access with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-6688 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (11th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-6688?: CVE-2026-6688 affects Elm-chan Fatfs. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-6688?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2026-6688 published?: CVE-2026-6688 was published on 2026-07-01 and last updated on 2026-07-02.

References

Affected products (1)

cpe:2.3:a:elm-chan:fatfs:*:*:*:*:*:*:*:*

More vulnerabilities in Elm-chan Fatfs

CVE-2026-6687 — High (CVSS 7.6): FatFs R0.16 and earlier contains a stack overflow bug in f_getlabel() because exFAT label length (XDIR_NumLabel) is…
CVE-2026-6682 — High (CVSS 7.6): In FatFS R0.16 and earlier contains a FAT32 integer overflow bug in mount_volume() where fasize *= fs->n_fats can wrap,…
CVE-2026-6685 — Medium (CVSS 6.1): FatFs R0.16 and earlier exhibits a stale dirty-cache skip via unsigned-subtraction wrap in f_read() / f_write()…
CVE-2026-6686 — Medium (CVSS 4.6): FatFs R0.16 and earlier contains an uninitialized cluster exposure when f_lseek() extends files beyond EOF without…
CVE-2026-6684 — Medium (CVSS 4.6): FatFs prior to R0.16 that use GPT scanning with 'FF_LBA64 = 1' contains an issue where an unbounded loop count derived…
CVE-2026-6683 — Medium (CVSS 4.6): FatFs R0.16 and earlier contains a divide-by-zero in exFAT sync logic bug when crafted metadata causes n_fatent - 2 to…

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