Exploitation evidence
Known exploited · CISA KEV listed
Added 2021-11-03. Ransomware campaign use: Unknown.
CISA required action: Apply updates per vendor instructions.
CISA due date: 2021-11-17. This is the catalog’s deadline, not an assessment of your organization’s exposure.
KEV checked 13 Nov 2026, 00:20 Jerusalem · Original catalog ↗Reported products and versions
Microsoft / Windows 10 Version 1809
Default status: Not specified
- affected: 10.0.0 to < 10.0.17763.1999 (custom)
Microsoft / Windows Server 2019
Default status: Not specified
- affected: 10.0.0 to < 10.0.17763.1999 (custom)
Microsoft / Windows Server 2019 (Server Core installation)
Default status: Not specified
- affected: 10.0.0 to < 10.0.17763.1999 (custom)
Microsoft / Windows 10 Version 1909
Default status: Not specified
- affected: 10.0.0 to < 10.0.18363.1621 (custom)
Microsoft / Windows 10 Version 21H1
Default status: Not specified
- affected: 10.0.0 to < 10.0.19043.1052 (custom)
Microsoft / Windows 10 Version 2004
Default status: Not specified
- affected: 10.0.0 to < 10.0.19041.1052 (custom)
Microsoft / Windows Server version 2004
Default status: Not specified
- affected: 10.0.0 to < 10.0.19041.1052 (custom)
Microsoft / Windows 10 Version 20H2
Default status: Not specified
- affected: 10.0.0 to < 10.0.19042.1052 (custom)
Microsoft / Windows Server version 20H2
Default status: Not specified
- affected: 10.0.0 to < 10.0.19042.1052 (custom)
Fixes and workarounds
No explicit solution text in the downloaded CVE record. Consult the vendor advisory; unaffected version ranges are shown above as reported, not inferred as a patch recommendation.
Sources and related reporting
Observed change timeline
History begins when Egret first downloads each source. It is not the complete upstream CVE history.
12 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-12",
"epss": 0.81107,
"percentile": 0.9964
}10 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-10",
"epss": 0.81107,
"percentile": 0.99638
}09 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-09",
"epss": 0.81107,
"percentile": 0.99637
}08 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-08",
"epss": 0.81107,
"percentile": 0.99637
}07 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-07",
"epss": 0.81107,
"percentile": 0.99637
}06 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-06",
"epss": 0.81107,
"percentile": 0.99636
}06 Nov 2026, 06:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-05",
"epss": 0.81107,
"percentile": 0.99636
}05 Nov 2026, 12:20 Jerusalem · CVE Program record changed
Stored CNA snapshot at this observation.
{
"containers": {
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"content": {
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"cpe:2.3:o:microsoft:windows_10_1809:10.0.17763.1999:*:*:*:*:*:arm64:*"
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"cpe:2.3:o:microsoft:windows_10_1909:10.0.18363.1621:*:*:*:*:*:x64:*",
"cpe:2.3:o:microsoft:windows_10_1809:10.0.18363.1621:*:*:*:*:*:x64:*"
],
"platforms": [
"32-bit Systems",
"x64-based Systems",
"ARM64-based Systems"
],
"product": "Windows 10 Version 1909",
"vendor": "Microsoft",
"versions": [
{
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"status": "affected",
"version": "10.0.0",
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]
},
{
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"cpe:2.3:o:microsoft:windows_10_21H1:10.0.19043.1052:*:*:*:*:*:x64:*",
"cpe:2.3:o:microsoft:windows_10_21H1:10.0.19043.1052:*:*:*:*:*:arm64:*",
"cpe:2.3:o:microsoft:windows_10_21H1:10.0.19043.1052:*:*:*:*:*:x86:*"
],
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"ARM64-based Systems",
"32-bit Systems"
],
"product": "Windows 10 Version 21H1",
"vendor": "Microsoft",
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"status": "affected",
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{
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"cpe:2.3:o:microsoft:windows_10_1809:10.0.19041.1052:*:*:*:*:*:x64:*"
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"32-bit Systems",
"ARM64-based Systems",
"x64-based Systems"
],
"product": "Windows 10 Version 2004",
"vendor": "Microsoft",
"versions": [
{
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"status": "affected",
"version": "10.0.0",
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]
},
{
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"cpe:2.3:o:microsoft:windows_server_2004:10.0.19041.1052:*:*:*:*:*:*:*"
],
"platforms": [
"x64-based Systems"
],
"product": "Windows Server version 2004",
"vendor": "Microsoft",
"versions": [
{
"lessThan": "10.0.19041.1052",
"status": "affected",
"version": "10.0.0",
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}
]
},
{
"cpes": [
"cpe:2.3:o:microsoft:windows_10_20H2:10.0.19042.1052:*:*:*:*:*:x86:*",
"cpe:2.3:o:microsoft:windows_10_20H2:10.0.19042.1052:*:*:*:*:*:arm64:*"
],
"platforms": [
"32-bit Systems",
"ARM64-based Systems"
],
"product": "Windows 10 Version 20H2",
"vendor": "Microsoft",
"versions": [
{
"lessThan": "10.0.19042.1052",
"status": "affected",
"version": "10.0.0",
"versionType": "custom"
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]
},
{
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"cpe:2.3:o:microsoft:windows_server_20H2:10.0.19042.1052:*:*:*:*:*:*:*"
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"x64-based Systems"
],
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"vendor": "Microsoft",
"versions": [
{
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"status": "affected",
"version": "10.0.0",
"versionType": "custom"
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]
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],
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"descriptions": [
{
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"value": "Windows Kernel Information Disclosure Vulnerability"
}
],
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"baseScore": 5.5,
"baseSeverity": "MEDIUM",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N/E:F/RL:O/RC:C",
"version": "3.1"
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{
"description": "Information Disclosure",
"lang": "en-US",
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]
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],
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"orgId": "f38d906d-7342-40ea-92c1-6c4a2c6478c8",
"shortName": "microsoft"
},
"references": [
{
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"x_refsource_MISC"
],
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}
],
"title": "Windows Kernel Information Disclosure Vulnerability"
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},
"cveMetadata": {
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"assignerShortName": "microsoft",
"cveId": "CVE-2021-31955",
"datePublished": "2021-06-08T22:46:25.000Z",
"dateReserved": "2021-04-30T00:00:00.000Z",
"dateUpdated": "2025-10-21T23:25:43.374Z",
"state": "PUBLISHED"
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"dataType": "CVE_RECORD",
"dataVersion": "5.1"
}04 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-04",
"epss": 0.81107,
"percentile": 0.99635
}03 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-03",
"epss": 0.81107,
"percentile": 0.99634
}03 Nov 2026, 02:22 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-02",
"epss": 0.81107,
"percentile": 0.99633
}03 Nov 2026, 02:22 Jerusalem · CISA KEV status changed
Stored KEV snapshot at this observation.
{
"cveID": "CVE-2021-31955",
"cwes": [
"CWE-497"
],
"dateAdded": "2021-11-03",
"dueDate": "2021-11-17",
"forensicTriage": "No",
"knownRansomwareCampaignUse": "Unknown",
"notes": "https://nvd.nist.gov/vuln/detail/CVE-2021-31955",
"product": "Windows",
"requiredAction": "Apply updates per vendor instructions.",
"shortDescription": "Microsoft Windows Kernel contains an unspecified vulnerability that allows for information disclosure. Successful exploitation allows attackers to read the contents of kernel memory from a user-mode process.",
"vendorProject": "Microsoft",
"vulnerabilityName": "Microsoft Windows Kernel Information Disclosure Vulnerability"
}