{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-21251", "assignerOrgId": "f38d906d-7342-40ea-92c1-6c4a2c6478c8", "state": "PUBLISHED", "assignerShortName": "microsoft", "dateReserved": "2025-12-11T21:02:05.736Z", "datePublished": "2026-02-10T17:51:40.939Z", "dateUpdated": "2026-02-10T20:38:42.933Z"}, "containers": {"cna": {"title": "Cluster Client Failover (CCF) Elevation of Privilege Vulnerability", "datePublic": "2026-02-10T08:00:00.000Z", "cpeApplicability": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:microsoft:windows_server_2019:*:*:*:*:*:*:*:*", "versionStartIncluding": "10.0.17763.0", "versionEndExcluding": "10.0.17763.8389"}, {"vulnerable": true, "criteria": "cpe:2.3:o:microsoft:windows_server_2019:*:*:*:*:*:*:*:*", "versionStartIncluding": "10.0.17763.0", "versionEndExcluding": "10.0.17763.8389"}, {"vulnerable": true, "criteria": "cpe:2.3:o:microsoft:windows_server_2022:*:*:*:*:*:*:*:*", "versionStartIncluding": "10.0.20348.0", "versionEndExcluding": "10.0.20348.4773"}, {"vulnerable": true, "criteria": "cpe:2.3:o:microsoft:windows_server_2025:*:*:*:*:*:*:*:*", "versionStartIncluding": "10.0.26100.0", "versionEndExcluding": "10.0.26100.32370"}, {"vulnerable": true, "criteria": "cpe:2.3:o:microsoft:windows_server_23h2:*:*:*:*:*:*:*:*", "versionStartIncluding": "10.0.25398.0", "versionEndExcluding": "10.0.25398.2149"}, {"vulnerable": true, "criteria": "cpe:2.3:o:microsoft:windows_server_2025:*:*:*:*:*:*:*:*", "versionStartIncluding": "10.0.26100.0", "versionEndExcluding": "10.0.26100.32370"}, {"vulnerable": true, "criteria": "cpe:2.3:o:microsoft:windows_server_2016:*:*:*:*:*:*:*:*", "versionStartIncluding": "10.0.14393.0", "versionEndExcluding": "10.0.14393.8868"}, {"vulnerable": true, "criteria": "cpe:2.3:o:microsoft:windows_server_2016:*:*:*:*:*:*:*:*", "versionStartIncluding": "10.0.14393.0", "versionEndExcluding": "10.0.14393.8868"}]}]}], "affected": [{"vendor": "Microsoft", "product": "Windows Server 2019", "platforms": ["x64-based Systems"], "versions": [{"version": "10.0.17763.0", "lessThan": "10.0.17763.8389", "versionType": "custom", "status": "affected"}]}, {"vendor": "Microsoft", "product": "Windows Server 2019 (Server Core installation)", "platforms": ["x64-based Systems"], "versions": [{"version": "10.0.17763.0", "lessThan": "10.0.17763.8389", "versionType": "custom", "status": "affected"}]}, {"vendor": "Microsoft", "product": "Windows Server 2022", "platforms": ["x64-based Systems"], "versions": [{"version": "10.0.20348.0", "lessThan": "10.0.20348.4773", "versionType": "custom", "status": "affected"}]}, {"vendor": "Microsoft", "product": "Windows Server 2025 (Server Core installation)", "platforms": ["x64-based Systems"], "versions": [{"version": "10.0.26100.0", "lessThan": "10.0.26100.32370", "versionType": "custom", "status": "affected"}]}, {"vendor": "Microsoft", "product": "Windows Server 2022, 23H2 Edition (Server Core installation)", "platforms": ["x64-based Systems"], "versions": [{"version": "10.0.25398.0", "lessThan": "10.0.25398.2149", "versionType": "custom", "status": "affected"}]}, {"vendor": "Microsoft", "product": "Windows Server 2025", "platforms": ["x64-based Systems"], "versions": [{"version": "10.0.26100.0", "lessThan": "10.0.26100.32370", "versionType": "custom", "status": "affected"}]}, {"vendor": "Microsoft", "product": "Windows Server 2016", "platforms": ["x64-based Systems"], "versions": [{"version": "10.0.14393.0", "lessThan": "10.0.14393.8868", "versionType": "custom", "status": "affected"}]}, {"vendor": "Microsoft", "product": "Windows Server 2016 (Server Core installation)", "platforms": ["x64-based Systems"], "versions": [{"version": "10.0.14393.0", "lessThan": "10.0.14393.8868", "versionType": "custom", "status": "affected"}]}], "descriptions": [{"value": "Use after free in Windows Cluster Client Failover allows an authorized attacker to elevate privileges locally.", "lang": "en-US"}], "problemTypes": [{"descriptions": [{"description": "CWE-416: Use After Free", "lang": "en-US", "type": "CWE", "cweId": "CWE-416"}]}], "providerMetadata": {"orgId": "f38d906d-7342-40ea-92c1-6c4a2c6478c8", "shortName": "microsoft", "dateUpdated": "2026-02-10T20:38:42.933Z"}, "references": [{"name": "Cluster Client Failover (CCF) Elevation of Privilege Vulnerability", "tags": ["vendor-advisory", "patch"], "url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21251"}], "metrics": [{"format": "CVSS", "scenarios": [{"lang": "en-US", "value": "GENERAL"}], "cvssV3_1": {"version": "3.1", "baseSeverity": "HIGH", "baseScore": 7.8, "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C"}}]}}}

{}

{"cveTags": [], "descriptions": [{"lang": "en", "value": "Use after free in Windows Cluster Client Failover allows an authorized attacker to elevate privileges locally."}], "id": "CVE-2026-21251", "lastModified": "2026-02-10T18:16:26.840", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "HIGH", "baseScore": 7.8, "baseSeverity": "HIGH", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "version": "3.1"}, "exploitabilityScore": 1.8, "impactScore": 5.9, "source": "secure@microsoft.com", "type": "Primary"}]}, "published": "2026-02-10T18:16:26.840", "references": [{"source": "secure@microsoft.com", "url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21251"}], "sourceIdentifier": "secure@microsoft.com", "vulnStatus": "Received", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-416"}], "source": "secure@microsoft.com", "type": "Primary"}]}

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