CVE-2026-6687

FatFs Stack Buffer Overflow via Uncapped exFAT Label Length

HIGH
7.6
CVSS Score
Published: July 1, 2026 at 01:57 PM UTC
Updated: October 25, 2026 at 05:10 PM UTC
2 products affected across 2 vendorsFatfsFatFs

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Severity
HIGH7.6
Exploit prediction
EPSS 0.3%
SSVC
PoC

Description

FatFs R0.16 and earlier contains a stack overflow bug in f_getlabel() because exFAT label length (XDIR_NumLabel) is trusted without enforcing spec maximums. This maps to CWE-121 (Stack-based Buffer Overflow). 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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v ≤ r0.16
v ≤ R0.16

Remediation

No guide yet

No remediation guidance has been written for this CVE yet, and no fixed version or vendor advisory is recorded against it.

References (4)

Third Party AdvisoryExploit
Source: cverecord
https://www.runzero.com/blog/fatfs-bugs/
Technical DescriptionThird Party AdvisoryExploit
Source: cverecord
https://github.com/runZeroInc/vulns-2026-fatfs-chance
Product
Source: cverecord
https://elm-chan.org/fsw/ff/

SSVC — Action Prioritization

SSVCPoCNot automatableTotal impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

7.6HIGHrunZero
Attack Vector
PHYSICAL
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
CHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
HIGH
Vector?

Quick Info

StatusANALYZED
CWE
CWE-121

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