CVE-2021-1691
Status: ModifiedHigh (7.7)—
Windows Hyper-V Denial of Service Vulnerability
CVSS
- Version: 3.1
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
- Base score: 7.7
Exploitation probability (EPSS)
- Probability of exploitation in the next 30 days: 4.07%
- Percentile among all scored CVEs: 91
- Score date: 10/15/2026
EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).
Affected technologies (2)
CWEs
- NVD-CWE-noinfo
References
Raw JSON (NVD)
Show
{
"id": "CVE-2021-1691",
"cveTags": [],
"metrics": {
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
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"role": "CISA Coordinator",
"options": [
{
"exploitation": "none"
},
{
"automatable": "no"
},
{
"technicalImpact": "partial"
}
],
"version": "2.0.3",
"timestamp": "2024-01-10T16:58:17.409213Z"
}
}
],
"cvssMetricV2": [
{
"type": "Primary",
"source": "nvd@nist.gov",
"cvssData": {
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"baseScore": 4,
"accessVector": "NETWORK",
"vectorString": "AV:N/AC:L/Au:S/C:N/I:N/A:P",
"authentication": "SINGLE",
"integrityImpact": "NONE",
"accessComplexity": "LOW",
"availabilityImpact": "PARTIAL",
"confidentialityImpact": "NONE"
},
"acInsufInfo": false,
"impactScore": 2.9,
"baseSeverity": "MEDIUM",
"obtainAllPrivilege": false,
"exploitabilityScore": 8,
"obtainUserPrivilege": false,
"obtainOtherPrivilege": false,
"userInteractionRequired": false
}
],
"cvssMetricV31": [
{
"type": "Secondary",
"source": "secure@microsoft.com",
"cvssData": {
"scope": "CHANGED",
"version": "3.1",
"baseScore": 7.7,
"attackVector": "NETWORK",
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H",
"integrityImpact": "NONE",
"userInteraction": "NONE",
"attackComplexity": "LOW",
"availabilityImpact": "HIGH",
"privilegesRequired": "LOW",
"confidentialityImpact": "NONE"
},
"impactScore": 4,
"exploitabilityScore": 3.1
},
{
"type": "Secondary",
"source": "nvd@nist.gov",
"cvssData": {
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"version": "3.1",
"baseScore": 7.7,
"attackVector": "NETWORK",
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H",
"integrityImpact": "NONE",
"userInteraction": "NONE",
"attackComplexity": "LOW",
"availabilityImpact": "HIGH",
"privilegesRequired": "LOW",
"confidentialityImpact": "NONE"
},
"impactScore": 4,
"exploitabilityScore": 3.1
}
]
},
"affected": [
{
"source": "secure@microsoft.com",
"affectedData": [
{
"cpes": [
"cpe:2.3:o:microsoft:windows_server_20H2:*:*:*:*:*:*:*:*"
],
"vendor": "Microsoft",
"product": "Windows Server version 20H2",
"versions": [
{
"status": "affected",
"version": "10.0.0",
"lessThan": "publication",
"versionType": "custom"
}
],
"platforms": [
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]
},
{
"cpes": [
"cpe:2.3:o:microsoft:windows_10_1909:*:*:*:*:*:*:x64:*"
],
"vendor": "Microsoft",
"product": "Windows 10 Version 1909",
"versions": [
{
"status": "affected",
"version": "10.0.0",
"lessThan": "publication",
"versionType": "custom"
}
],
"platforms": [
"x64-based Systems"
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},
{
"cpes": [
"cpe:2.3:o:microsoft:windows_server_1909:*:*:*:*:*:*:*:*"
],
"vendor": "Microsoft",
"product": "Windows Server, version 1909 (Server Core installation)",
"versions": [
{
"status": "affected",
"version": "10.0.0",
"lessThan": "publication",
"versionType": "custom"
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],
"platforms": [
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},
{
"cpes": [
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],
"vendor": "Microsoft",
"product": "Windows 10 Version 2004",
"versions": [
{
"status": "affected",
"version": "10.0.0",
"lessThan": "publication",
"versionType": "custom"
}
],
"platforms": [
"x64-based Systems"
]
},
{
"cpes": [
"cpe:2.3:o:microsoft:windows_server_2004:*:*:*:*:*:*:*:*"
],
"vendor": "Microsoft",
"product": "Windows Server version 2004",
"versions": [
{
"status": "affected",
"version": "10.0.0",
"lessThan": "publication",
"versionType": "custom"
}
],
"platforms": [
"x64-based Systems"
]
}
]
}
],
"published": "2021-01-12T20:15:33.353",
"references": [
{
"url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-1691",
"source": "secure@microsoft.com"
},
{
"url": "https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-1691",
"source": "af854a3a-2127-422b-91ae-364da2661108"
}
],
"vulnStatus": "Modified",
"weaknesses": [
{
"type": "Primary",
"source": "nvd@nist.gov",
"description": [
{
"lang": "en",
"value": "NVD-CWE-noinfo"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "Windows Hyper-V Denial of Service Vulnerability"
},
{
"lang": "es",
"value": "Una Vulnerabilidad de Denegación de Servicio de Hyper-V. Este ID de CVE es diferente de CVE-2021-1692"
}
],
"lastModified": "2026-06-17T03:32:20.863",
"configurations": [
{
"nodes": [
{
"negate": false,
"cpeMatch": [
{
"criteria": "cpe:2.3:o:microsoft:windows_10:20h2:*:*:*:*:*:*:*",
"vulnerable": true,
"matchCriteriaId": "9E2C378B-1507-4C81-82F6-9F599616845A"
},
{
"criteria": "cpe:2.3:o:microsoft:windows_10:1909:*:*:*:*:*:*:*",
"vulnerable": true,
"matchCriteriaId": "E9273B95-20ED-4547-B0A8-95AD15B30372"
},
{
"criteria": "cpe:2.3:o:microsoft:windows_10:2004:*:*:*:*:*:*:*",
"vulnerable": true,
"matchCriteriaId": "AAE74AF3-C559-4645-A6C0-25C3D647AAC8"
},
{
"criteria": "cpe:2.3:o:microsoft:windows_server_2016:20h2:*:*:*:*:*:*:*",
"vulnerable": true,
"matchCriteriaId": "4A190388-AA82-4504-9D5A-624F23268C9F"
},
{
"criteria": "cpe:2.3:o:microsoft:windows_server_2016:1909:*:*:*:*:*:*:*",
"vulnerable": true,
"matchCriteriaId": "C253A63F-03AB-41CB-A03A-B2674DEA98AA"
},
{
"criteria": "cpe:2.3:o:microsoft:windows_server_2016:2004:*:*:*:*:*:*:*",
"vulnerable": true,
"matchCriteriaId": "0B60D940-80C7-49F0-8F4E-3F99AC15FA82"
}
],
"operator": "OR"
}
]
}
],
"sourceIdentifier": "secure@microsoft.com"
}