How severe is CVE-2026-6685?

CVE-2026-6685 has a CVSS 3.x base score of 6.1, rated medium severity. It is exploitable over physical access with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability high.

Is CVE-2026-6685 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-2026-6685?

CVE-2026-6685 affects Elm-chan Fatfs. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-6685?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2026-6685 published?

CVE-2026-6685 was published on 2026-07-01 and last updated on 2026-07-02.

CVE-2026-6685

CVE-2026-6685 is a medium-severity vulnerability in Elm-chan Fatfs with a CVSS 3.x base score of 6.1. 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-191.

Key facts

Severity: Medium (CVSS 3.x base score 6.1)
EPSS exploit prediction: 0% (11th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-191
Affected product: Elm-chan Fatfs
Published: 2026-07-01
Last modified: 2026-07-02

Description

FatFs R0.16 and earlier exhibits a stale dirty-cache skip via unsigned-subtraction wrap in f_read() / f_write() (fp->sect - sect < cc) during interleaved read/write on fragmented filesystems. This maps to CWE-191 (Integer Underflow). Estimated CVSS v3.1 vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H (6.1, Medium). The estimated CISA SSVC vectors are Exploitation: PoC, Technical Impact: Total.

Frequently asked questions

What is CVE-2026-6685?: FatFs R0.16 and earlier exhibits a stale dirty-cache skip via unsigned-subtraction wrap in f_read() / f_write() (fp->sect - sect < cc) during interleaved read/write on fragmented filesystems. This maps to CWE-191 (Integer Underflow). Estimated CVSS v3.1 vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H (6.1, Medium). The estimated CISA SSVC vectors are Exploitation: PoC, Technical Impact: Total.
How severe is CVE-2026-6685?: CVE-2026-6685 has a CVSS 3.x base score of 6.1, rated medium severity. It is exploitable over physical access with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability high.
Is CVE-2026-6685 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-2026-6685?: CVE-2026-6685 affects Elm-chan Fatfs. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-6685?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2026-6685 published?: CVE-2026-6685 was published on 2026-07-01 and last updated on 2026-07-02.

References

Affected products (1)

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

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Browse all CWE-191 (Integer Underflow) vulnerabilities →