CVE-2026-20856

{"id": "CVE-2026-20856", "cveTags": [], "metrics": {"ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-20856", "role": "CISA Coordinator", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "total"}], "version": "2.0.3", "timestamp": "2026-01-14T04:56:08.248762Z"}}], "cvssMetricV31": [{"type": "Secondary", "source": "secure@microsoft.com", "cvssData": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 8.1, "attackVector": "NETWORK", "baseSeverity": "HIGH", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H", "integrityImpact": "HIGH", "userInteraction": "NONE", "attackComplexity": "HIGH", "availabilityImpact": "HIGH", "privilegesRequired": "NONE", "confidentialityImpact": "HIGH"}, "impactScore": 5.9, "exploitabilityScore": 2.2}]}, "affected": [{"source": "secure@microsoft.com", "affectedData": [{"vendor": "Microsoft", "product": "Windows 10 Version 1607", "versions": [{"status": "affected", "version": "10.0.14393.0", "lessThan": "10.0.14393.8783", "versionType": "custom"}], "platforms": ["32-bit Systems", "x64-based Systems"]}, {"vendor": "Microsoft", "product": "Windows 10 Version 1809", "versions": [{"status": "affected", "version": "10.0.17763.0", "lessThan": "10.0.17763.8276", "versionType": "custom"}], "platforms": ["32-bit Systems", "x64-based Systems"]}, {"vendor": "Microsoft", "product": "Windows 10 Version 21H2", "versions": [{"status": "affected", "version": "10.0.19044.0", "lessThan": "10.0.19044.6809", "versionType": "custom"}], "platforms": ["32-bit Systems", "ARM64-based Systems", "x64-based Systems"]}, {"vendor": "Microsoft", "product": "Windows 10 Version 22H2", "versions": [{"status": "affected", "version": "10.0.19045.0", "lessThan": "10.0.19045.6809", "versionType": "custom"}], "platforms": ["32-bit Systems", "ARM64-based Systems", "x64-based Systems"]}, {"vendor": "Microsoft", "product": "Windows 11 version 23H2", "versions": [{"status": "affected", "version": "10.0.22631.0", "lessThan": "10.0.22631.6491", "versionType": "custom"}], "platforms": ["ARM64-based Systems"]}, {"vendor": "Microsoft", "product": "Windows 11 Version 23H2", "versions": [{"status": "affected", "version": "10.0.22631.0", "lessThan": "10.0.22631.6491", "versionType": "custom"}], "platforms": ["x64-based Systems"]}, {"vendor": "Microsoft", "product": "Windows 11 Version 24H2", "versions": [{"status": "affected", "version": "10.0.26100.0", "lessThan": "10.0.26100.7623", "versionType": "custom"}], "platforms": ["ARM64-based Systems", "x64-based Systems"]}, {"vendor": "Microsoft", "product": "Windows 11 Version 25H2", "versions": [{"status": "affected", "version": "10.0.26200.0", "lessThan": "10.0.26200.7623", "versionType": "custom"}], "platforms": ["ARM64-based Systems", "x64-based Systems"]}, {"vendor": "Microsoft", "product": "Windows Server 2012", "versions": [{"status": "affected", "version": "6.2.9200.0", "lessThan": "6.2.9200.25868", "versionType": "custom"}], "platforms": ["x64-based Systems"]}, {"vendor": "Microsoft", "product": "Windows Server 2012 (Server Core installation)", "versions": [{"status": "affected", "version": "6.2.9200.0", "lessThan": "6.2.9200.25868", "versionType": "custom"}], "platforms": ["x64-based Systems"]}, {"vendor": "Microsoft", "product": "Windows Server 2012 R2", "versions": [{"status": "affected", "version": "6.3.9600.0", "lessThan": "6.3.9600.22968", "versionType": "custom"}], "platforms": ["x64-based Systems"]}, {"vendor": "Microsoft", "product": "Windows Server 2012 R2 (Server Core installation)", "versions": [{"status": "affected", "version": "6.3.9600.0", "lessThan": "6.3.9600.22968", "versionType": "custom"}], "platforms": ["x64-based Systems"]}, {"vendor": "Microsoft", "product": "Windows Server 2016", "versions": [{"status": "affected", "version": "10.0.14393.0", "lessThan": "10.0.14393.8783", "versionType": "custom"}], "platforms": ["x64-based Systems"]}, {"vendor": "Microsoft", "product": "Windows Server 2016 (Server Core installation)", "versions": [{"status": "affected", "version": "10.0.14393.0", "lessThan": "10.0.14393.8783", "versionType": "custom"}], "platforms": ["x64-based Systems"]}, {"vendor": "Microsoft", "product": "Windows Server 2019", "versions": [{"status": "affected", "version": "10.0.17763.0", "lessThan": "10.0.17763.8276", "versionType": "custom"}], "platforms": ["x64-based Systems"]}, {"vendor": "Microsoft", "product": "Windows Server 2019 (Server Core installation)", "versions": [{"status": "affected", "version": "10.0.17763.0", "lessThan": "10.0.17763.8276", "versionType": "custom"}], "platforms": ["x64-based Systems"]}, {"vendor": "Microsoft", "product": "Windows Server 2022", "versions": [{"status": "affected", "version": "10.0.20348.0", "lessThan": "10.0.20348.4648", "versionType": "custom"}], "platforms": ["x64-based Systems"]}, {"vendor": "Microsoft", "product": "Windows Server 2022, 23H2 Edition (Server Core installation)", "versions": [{"status": "affected", "version": "10.0.25398.0", "lessThan": "10.0.25398.2092", "versionType": "custom"}], "platforms": ["x64-based Systems"]}, {"vendor": "Microsoft", "product": "Windows Server 2025", "versions": [{"status": "affected", "version": "10.0.26100.0", "lessThan": "10.0.26100.32230", "versionType": "custom"}], "platforms": ["x64-based Systems"]}, {"vendor": "Microsoft", "product": "Windows Server 2025 (Server Core installation)", "versions": [{"status": "affected", "version": "10.0.26100.0", "lessThan": "10.0.26100.32230", "versionType": "custom"}], "platforms": ["x64-based Systems"]}]}], "published": "2026-01-13T18:16:14.313", "references": [{"url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20856", "tags": ["Vendor Advisory"], "source": "secure@microsoft.com"}], "vulnStatus": "Analyzed", "weaknesses": [{"type": "Secondary", "source": "secure@microsoft.com", "description": [{"lang": "en", "value": "CWE-20"}]}], "descriptions": [{"lang": "en", "value": "Improper input validation in Windows Server Update Service allows an unauthorized attacker to execute code over a network."}, {"lang": "es", "value": "La validaci\u00f3n de entrada indebida en Windows Servidor Update Service permite a un atacante no autorizado ejecutar c\u00f3digo a trav\u00e9s de una red."}], "lastModified": "2026-07-30T21:17:04.020", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:o:microsoft:windows_10_1607:*:*:*:*:*:*:x64:*", "vulnerable": true, "matchCriteriaId": "9A956D23-259E-450B-8406-FEB2BBED1F39", "versionEndExcluding": "10.0.14393.8783"}, {"criteria": "cpe:2.3:o:microsoft:windows_10_1607:*:*:*:*:*:*:x86:*", "vulnerable": true, "matchCriteriaId": "41D387B9-5E9D-47CB-B044-D7D10FFFB458", "versionEndExcluding": "10.0.14393.8783"}, {"criteria": "cpe:2.3:o:microsoft:windows_10_1809:*:*:*:*:*:*:x64:*", "vulnerable": true, "matchCriteriaId": "DD4CBDAB-7626-4048-8474-B1BD9C1F3255", "versionEndExcluding": "10.0.17763.8276"}, {"criteria": "cpe:2.3:o:microsoft:windows_10_1809:*:*:*:*:*:*:x86:*", "vulnerable": true, "matchCriteriaId": "A6D4C631-2CC0-407C-9ACA-7C151006598C", "versionEndExcluding": "10.0.17763.8276"}, {"criteria": "cpe:2.3:o:microsoft:windows_10_21h2:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "1895E186-5B2E-43CC-AF1F-B5C95419D8C5", "versionEndExcluding": "10.0.19044.6809"}, {"criteria": "cpe:2.3:o:microsoft:windows_10_22h2:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "B7CB5184-1BA1-4D71-8AE3-CF4C6B63A469", "versionEndExcluding": "10.0.19045.6809"}, {"criteria": "cpe:2.3:o:microsoft:windows_11_23h2:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "8D675DAA-4DCE-4727-BE5F-C954BBD252C4", "versionEndExcluding": "10.0.22631.6491"}, {"criteria": "cpe:2.3:o:microsoft:windows_11_24h2:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "D249551B-1433-4E5E-A587-40F782E91E09", "versionEndExcluding": "10.0.26100.7623"}, {"criteria": 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