CVE-2026-6688Public exploit

Memory corruption via unbounded LFN filename copy

Published Jul 1, 2026 · Updated Jul 1, 2026

Buffer overflow in downstream filename handling for ChaN FatFs R0.16 and earlier allows attackers to corrupt memory via a crafted FAT volume. With LFN enabled, f_readdir() returns up to 255 characters in fno.fname, while affected callers use strcpy or sprintf to copy it into shorter fixed buffers without checking its length. The target must traverse an attacker-controlled FAT directory; consequences range from a crash to code execution according to the downstream buffer and platform protections.

CVSS severity7.6
High
EPSS probability0.32%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Buffer overflow in downstream filename handling for ChaN FatFs R0.16 and earlier allows attackers to corrupt memory via a crafted FAT volume. With LFN enabled, f_readdir() returns up to 255 characters in fno.fname, while affected callers use strcpy or sprintf to copy it into shorter fixed buffers without checking its length. The target must traverse an attacker-controlled FAT directory; consequences range from a crash to code execution according to the downstream buffer and platform protections.

The record

CVE
CVE-2026-6688
Published
Jul 1, 2026
Updated
Jul 1, 2026
Vendor
ChaN
Product
FatFs
Classifications
CWE-120, T1200
Attack vector
physical
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 1, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 1, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <=R0.16

What conditions does exploitation require?

Attack vectorphysical
Required privilegesunauthenticated

What is affected?

ChaN · FatFsversion=0 <=R0.16

Published CVSS scores

7.6runZeroCVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorphysical
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-120Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
T1200Hardware Additions

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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