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CVE-2026-6688

FatFs Buffer Overflow via Unbounded LFN Filename Copy

Published: Jul 1, 2026Updated: Jul 2, 2026 Sources: CVE List NVDCWE-120
7.6HIGH
NVD MITRE
EPSS Score
0.2%
Top 88.7%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
No Fix Available
Self-Check
Not available

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.

No summary for this CVE yet.

CVSS Vector Breakdown

AV:PAC:LPR:NUI:NS:CC:HI:HA:H
Exploitability
AV:PAttack Vector
Physical
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:CScope
Changed
Impact
C:HConfidentiality
High
I:HIntegrity
High
A:HAvailability
High
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Weaknesses

CWE-120

Affected Products

elm-chan
fatfs
ChaN
FatFs

Exploitability

No known exploits, KEV entries, or remediation guidance available for this vulnerability yet.
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Attack Graph

Products CVE Techniques Tactics

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MITRE ATT&CK

2 techniques
Initial Access
Privilege Escalation
View detailed technique mapping

References

https://elm-chan.org/fsw/ff/
elm-chan.org
https://github.com/runZeroInc/vulns-2026-fatfs-chance
github.com
https://www.runzero.com/advisories/fatfs-long-fn-of-downstream-cve-2026-6688/
runzero.com
and 1 more references View all →
News mentions
3

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