TI-2026-05867 Aliases CVE-2026-6688 GHSA-8vm2-mjff-2gg2

FatFs Buffer Overflow via Unbounded LFN Filename Copy

HIGH 68CWE-120Published 2026-07-01 · Updated 2026-07-01

Key facts

Attack vector: Physical
Privileges required: None
User interaction: None
Attack complexity: Low
Impact type: Code execution
Confidentiality · integrity · availability: High · High · High
Fix status: No fix listed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-120 and the CVSS impact.

Summary

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV

EPSS 0.00322 25th percentileScored 2026-11-07

Public exploit Yes 2 exploit referencesTagged by NVD

Fix No fix listed No fixed version in the sources yet

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: Poc
Automatable: No
Technical impact: Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
ChaN	FatFs	up to R0.16	—	No fix listed	CNA

FatFs VendorChaN Affected up to R0.16 Fixed in — No fix listed CNA

CPE configurations NVD · 1

CPE	Versions	Role	Vendor
cpe:2.3:a:elm-chan:fatfs::::::::	up to r0.16	Vulnerable	ChaN

cpe:2.3:a:elm-chan:fatfs:*:*:*:*:*:*:*:* Versions up to r0.16 Vulnerable ·ChaN

Remediation

No fixed version listed by the sources yet.

Timeline

2026-10-02 Threatist record created from CVE-2026-6688
2026-10-03 Alias added: GHSA-8vm2-mjff-2gg2

References

Exploit 2

Advisory 1

https://www.runzero.com/advisories/fatfs-long-fn-of-downstream-cve-2026-6688/

Other 1

https://elm-chan.org/fsw/ff/

TI-2026-05866 FatFs Stack Buffer Overflow via Uncapped exFAT Label Length CVSS 3.1HIGH 7.6
TI-2026-05862 FatFs Integer Overflow in FAT32 Volume Mount CVSS 3.1HIGH 7.6
TI-2026-05865 FatFs Use of Uninitialized Clusters After Seek Past EOF CVSS 3.1MEDIUM 4.6
TI-2026-05864 FatFs Infinite Loop in GPT Partition Scan CVSS 3.1MEDIUM 4.6
TI-2026-05863 FatFs Divide-by-Zero in exFAT Sync CVSS 3.1MEDIUM 4.6

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences