{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-6686", "assignerOrgId": "44488dab-36db-4358-99f9-bc116477f914", "state": "PUBLISHED", "assignerShortName": "runZero", "dateReserved": "2026-04-20T15:06:22.242Z", "datePublished": "2026-07-01T13:55:09.072Z", "dateUpdated": "2026-07-01T15:05:27.926Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "44488dab-36db-4358-99f9-bc116477f914", "shortName": "runZero", "dateUpdated": "2026-07-01T13:55:09.072Z"}, "title": "FatFs Use of Uninitialized Clusters After Seek Past EOF", "datePublic": "2026-07-01T13:00:00.000Z", "problemTypes": [{"descriptions": [{"lang": "en", "cweId": "CWE-908", "description": "CWE-908 Use of uninitialized resource", "type": "CWE"}]}], "affected": [{"vendor": "ChaN", "product": "FatFs", "versions": [{"status": "affected", "version": "0", "lessThanOrEqual": "R0.16", "versionType": "custom"}], "defaultStatus": "unaffected"}], "descriptions": [{"lang": "en", "value": "FatFs R0.16 and earlier contains an uninitialized cluster exposure when f_lseek() extends files beyond EOF without zero-filling newly allocated clusters. This maps to CWE-908 (Use of Uninitialized Resource). Estimated CVSS v3.1 vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N (4.6, Medium). The estimated CISA SSVC vectors are Exploitation: PoC, Technical Impact: Partial.", "supportingMedia": [{"type": "text/html", "base64": false, "value": "FatFs R0.16 and earlier contains an uninitialized cluster exposure when f_lseek() extends files beyond EOF without zero-filling newly allocated clusters. This maps to CWE-908 (Use of Uninitialized Resource). Estimated CVSS v3.1 vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N (4.6, Medium). The estimated CISA SSVC vectors are Exploitation: PoC, Technical Impact: Partial."}]}], "references": [{"url": "https://www.runzero.com/blog/fatfs-bugs/", "tags": ["third-party-advisory"]}, {"url": "https://github.com/runZeroInc/vulns-2026-fatfs-chance", "tags": ["technical-description"]}, {"url": "https://elm-chan.org/fsw/ff/", "tags": ["product"]}, {"url": "https://www.runzero.com/advisories/fatfs-uninit-cluster-exposure-cve-2026-6686/", "tags": ["third-party-advisory"]}], "metrics": [{"format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}], "cvssV3_1": {"version": "3.1", "attackVector": "PHYSICAL", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "availabilityImpact": "NONE", "baseSeverity": "MEDIUM", "baseScore": 4.6, "vectorString": "CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N"}}], "credits": [{"lang": "en", "value": "HD Moore of runZero, Inc.", "type": "finder"}, {"lang": "en", "value": "Tod Beardsley of runZero, Inc.", "type": "coordinator"}], "source": {"discovery": "UNKNOWN"}, "x_generator": {"engine": "Vulnogram 1.0.2"}}, "adp": [{"references": [{"url": "https://github.com/runZeroInc/vulns-2026-fatfs-chance", "tags": ["exploit"]}], "metrics": [{"other": {"type": "ssvc", "content": {"timestamp": "2026-07-01T15:05:23.138301Z", "id": "CVE-2026-6686", "options": [{"Exploitation": "poc"}, {"Automatable": "no"}, {"Technical Impact": "partial"}], "role": "CISA Coordinator", "version": "2.0.3"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-07-01T15:05:27.926Z"}}]}}

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