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CVE-2026-6688

Elm-chan Fatfs buffer overflow

7.6 HIGHPublic exploitEPSS 0.32%
  1. Published1 Jul 2026

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.

CVSS 3.1 breakdown

Attack vectorPhysical
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeChanged
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

Affected products

Elm-chan Fatfs≤ r0.16

Remediation

No fixed version is recorded in the NVD data. Check the vendor advisory for the latest guidance.

References

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Frequently asked

Is CVE-2026-6688 being actively exploited?

CVE-2026-6688 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.32%.

How severe is CVE-2026-6688?

CVE-2026-6688 has a CVSS 3.1 base score of 7.6, rated high. EPSS estimates a 0.32% probability of exploitation.

Which products are affected by CVE-2026-6688?

Affected products include Elm-chan Fatfs.

How do I fix CVE-2026-6688?

Apply the vendor's patch or advisory guidance, then verify no affected versions remain across your devices.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-6688 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.