CVE-2026-6686Public exploit

Stale data disclosure via uncleared file clusters

Published Jul 1, 2026 · Updated Jul 1, 2026

Information disclosure in ChaN FatFs R0.16 and earlier allows local users to read stale on-media data from extended files. The ff.c f_lseek() path grows the cluster chain and logical file size without clearing newly allocated sectors, exposing residual deleted-file contents. Reachability requires read access to a file that an application has extended with a seek; the primary exposure is local or physical.

CVSS severity4.6
Medium
EPSS probability0.26%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Information disclosure in ChaN FatFs R0.16 and earlier allows local users to read stale on-media data from extended files. The ff.c f_lseek() path grows the cluster chain and logical file size without clearing newly allocated sectors, exposing residual deleted-file contents. Reachability requires read access to a file that an application has extended with a seek; the primary exposure is local or physical.

The record

CVE
CVE-2026-6686
Published
Jul 1, 2026
Updated
Jul 1, 2026
Vendor
ChaN
Product
FatFs
Classifications
CWE-908, T1005
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

4.6runZeroCVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorphysical
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-908Use of Uninitialized Resource
T1005Data from Local System

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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