CVE-2026-6687

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.

CVSS v3 7.6 HIGH

7.6^/10

CVSS v3 : HIGH

Vector :

Exploitability : 0.9 / Impact : 6.0

Attack Vector PHYSICAL

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact HIGH

Integrity Impact HIGH

Availability Impact HIGH

Scope CHANGED

References

Link	Resource
https://elm-chan.org/fsw/ff/	Product
https://github.com/runZeroInc/vulns-2026-fatfs-chance	Third Party Advisory Exploit
https://www.runzero.com/advisories/fatfs-exfat-label-len-of-cve-2026-6687/	Third Party Advisory
https://www.runzero.com/blog/fatfs-bugs/	Third Party Advisory Exploit
https://github.com/runZeroInc/vulns-2026-fatfs-chance	Third Party Advisory Exploit

Configurations

Configuration 1 (hide)

cpe:2.3:a:elm-chan:fatfs:*:*:*:*:*:*:*:*

History

02 Jul 2026, 14:38

Type	Values Removed	Values Added
First Time		Elm-chan Elm-chan fatfs
CPE		cpe:2.3:a:elm-chan:fatfs::::::::
References	~~() https://elm-chan.org/fsw/ff/ -~~	() https://elm-chan.org/fsw/ff/ - Product
References	~~() https://github.com/runZeroInc/vulns-2026-fatfs-chance -~~	() https://github.com/runZeroInc/vulns-2026-fatfs-chance - Third Party Advisory, Exploit
References	~~() https://www.runzero.com/advisories/fatfs-exfat-label-len-of-cve-2026-6687/ -~~	() https://www.runzero.com/advisories/fatfs-exfat-label-len-of-cve-2026-6687/ - Third Party Advisory
References	~~() https://www.runzero.com/blog/fatfs-bugs/ -~~	() https://www.runzero.com/blog/fatfs-bugs/ - Third Party Advisory, Exploit

01 Jul 2026, 16:16

Type	Values Removed	Values Added
References	~~() https://github.com/runZeroInc/vulns-2026-fatfs-chance -~~	() https://github.com/runZeroInc/vulns-2026-fatfs-chance -

01 Jul 2026, 15:17

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-07-01 15:17

Updated : 2026-07-02 14:38

NVD link : CVE-2026-6687

Mitre link : CVE-2026-6687

CVE.ORG link : CVE-2026-6687

JSON object : View

Products Affected

elm-chan

fatfs

CWE

CWE-121

Stack-based Buffer Overflow

{"id": "CVE-2026-6687", "cveTags": [], "metrics": {"ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-6687", "role": "CISA Coordinator", "options": [{"exploitation": "poc"}, {"automatable": "no"}, {"technicalImpact": "total"}], "version": "2.0.3", "timestamp": "2026-07-01T15:06:20.995228Z"}}], "cvssMetricV31": [{"type": "Secondary", "source": "44488dab-36db-4358-99f9-bc116477f914", "cvssData": {"scope": "CHANGED", "version": "3.1", "baseScore": 7.6, "attackVector": "PHYSICAL", "baseSeverity": "HIGH", "vectorString": "CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H", "integrityImpact": "HIGH", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "HIGH", "privilegesRequired": "NONE", "confidentialityImpact": "HIGH"}, "impactScore": 6.0, "exploitabilityScore": 0.9}]}, "affected": [{"source": "44488dab-36db-4358-99f9-bc116477f914", "affectedData": [{"vendor": "ChaN", "product": "FatFs", "versions": [{"status": "affected", "version": "0", "versionType": "custom", "lessThanOrEqual": "R0.16"}], "defaultStatus": "unaffected"}]}], "published": "2026-07-01T15:17:12.870", "references": [{"url": "https://elm-chan.org/fsw/ff/", "tags": ["Product"], "source": "44488dab-36db-4358-99f9-bc116477f914"}, {"url": "https://github.com/runZeroInc/vulns-2026-fatfs-chance", "tags": ["Third Party Advisory", "Exploit"], "source": "44488dab-36db-4358-99f9-bc116477f914"}, {"url": "https://www.runzero.com/advisories/fatfs-exfat-label-len-of-cve-2026-6687/", "tags": ["Third Party Advisory"], "source": "44488dab-36db-4358-99f9-bc116477f914"}, {"url": "https://www.runzero.com/blog/fatfs-bugs/", "tags": ["Third Party Advisory", "Exploit"], "source": "44488dab-36db-4358-99f9-bc116477f914"}, {"url": "https://github.com/runZeroInc/vulns-2026-fatfs-chance", "tags": ["Third Party Advisory", "Exploit"], "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0"}], "vulnStatus": "Analyzed", "weaknesses": [{"type": "Secondary", "source": "44488dab-36db-4358-99f9-bc116477f914", "description": [{"lang": "en", "value": "CWE-121"}]}], "descriptions": [{"lang": "en", "value": "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."}], "lastModified": "2026-07-02T14:38:40.173", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:a:elm-chan:fatfs:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "B99160BB-C4F5-4DA0-9FC9-0723E0633E00", "versionEndIncluding": "r0.16"}], "operator": "OR"}]}], "sourceIdentifier": "44488dab-36db-4358-99f9-bc116477f914"}