Exploitation evidence
Known exploited · CISA KEV listed
Added 2021-11-03. Ransomware campaign use: Known.
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 1507
Default status: Not specified
- affected: 10.0.10240.0 to < 10.0.10240.19060 (custom)
Microsoft / Windows 10 Version 1607
Default status: Not specified
- affected: 10.0.14393.0 to < 10.0.14393.4651 (custom)
Microsoft / Windows 10 Version 1809
Default status: Not specified
- affected: 10.0.17763.0 to < 10.0.17763.2183 (custom)
Microsoft / Windows 10 Version 1809
Default status: Not specified
- affected: 10.0.0 to < 10.0.17763.2183 (custom)
Microsoft / Windows 10 Version 1909
Default status: Not specified
- affected: 10.0.0 to < 10.0.18363.1801 (custom)
Microsoft / Windows 10 Version 2004
Default status: Not specified
- affected: 10.0.0 to < 10.0.19041.1237 (custom)
Microsoft / Windows 10 Version 20H2
Default status: Not specified
- affected: 10.0.0 to < 10.0.19042.1237 (custom)
Microsoft / Windows 10 Version 21H1
Default status: Not specified
- affected: 10.0.0 to < 10.0.19043.1237 (custom)
Microsoft / Windows 7
Default status: Not specified
- affected: 6.1.0 to < 6.1.7601.25712 (custom)
Microsoft / Windows 7 Service Pack 1
Default status: Not specified
- affected: 6.1.0 to < 6.1.7601.25712 (custom)
Microsoft / Windows 8.1
Default status: Not specified
- affected: 6.3.0 to < 6.3.9600.20120 (custom)
Microsoft / Windows Server 2008 R2 Service Pack 1
Default status: Not specified
- affected: 6.1.7601.0 to < 6.1.7601.25712 (custom)
Microsoft / Windows Server 2008 R2 Service Pack 1 (Server Core installation)
Default status: Not specified
- affected: 6.1.7601.0 to < 6.1.7601.25712 (custom)
Microsoft / Windows Server 2008 Service Pack 2
Default status: Not specified
- affected: 6.0.6003.0 to < 6.0.6003.21218 (custom)
Microsoft / Windows Server 2008 Service Pack 2 (Server Core installation)
Default status: Not specified
- affected: 6.0.6003.0 to < 6.0.6003.21218 (custom)
Microsoft / Windows Server 2012
Default status: Not specified
- affected: 6.2.9200.0 to < 6.2.9200.23462 (custom)
Microsoft / Windows Server 2012 (Server Core installation)
Default status: Not specified
- affected: 6.2.9200.0 to < 6.2.9200.23462 (custom)
Microsoft / Windows Server 2012 R2
Default status: Not specified
- affected: 6.3.9600.0 to < 6.3.9600.20120 (custom)
Microsoft / Windows Server 2012 R2 (Server Core installation)
Default status: Not specified
- affected: 6.3.9600.0 to < 6.3.9600.20120 (custom)
Microsoft / Windows Server 2016
Default status: Not specified
- affected: 10.0.14393.0 to < 10.0.14393.4651 (custom)
Microsoft / Windows Server 2016 (Server Core installation)
Default status: Not specified
- affected: 10.0.14393.0 to < 10.0.14393.4651 (custom)
Microsoft / Windows Server 2019
Default status: Not specified
- affected: 10.0.17763.0 to < 10.0.17763.2183 (custom)
Microsoft / Windows Server 2019 (Server Core installation)
Default status: Not specified
- affected: 10.0.17763.0 to < 10.0.17763.2183 (custom)
Microsoft / Windows Server 2022
Default status: Not specified
- affected: 10.0.20348.0 to < 10.0.20348.230 (custom)
Microsoft / Windows Server version 2004
Default status: Not specified
- affected: 10.0.0 to < 10.0.19041.1237 (custom)
Microsoft / Windows Server version 20H2
Default status: Not specified
- affected: 10.0.0 to < 10.0.19042.1237 (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
CVE Program record ↗ · Download tracked evidence as JSON
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-40444
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-40444
- http://packetstormsecurity.com/files/164210/Microsoft-Windows-MSHTML-Overview.html
- http://packetstormsecurity.com/files/165214/Microsoft-Office-Word-MSHTML-Remote-Code-Execution.html
- http://packetstormsecurity.com/files/167317/Microsoft-Office-MSDT-Follina-Proof-Of-Concept.html
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-40444
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": 0.9784,
"percentile": 0.99908
}10 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-10",
"epss": 0.9784,
"percentile": 0.99907
}09 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-09",
"epss": 0.9784,
"percentile": 0.99907
}08 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-08",
"epss": 0.9784,
"percentile": 0.99907
}07 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-07",
"epss": 0.9784,
"percentile": 0.99907
}06 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-06",
"epss": 0.9784,
"percentile": 0.99907
}06 Nov 2026, 06:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-05",
"epss": 0.9784,
"percentile": 0.99907
}05 Nov 2026, 06:20 Jerusalem · CVE Program record changed
Stored CNA snapshot at this observation.
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"datePublic": "2021-09-07T14:00:00.000Z",
"descriptions": [
{
"lang": "en-US",
"value": "Microsoft is investigating reports of a remote code execution vulnerability in MSHTML that affects Microsoft Windows. Microsoft is aware of targeted attacks that attempt to exploit this vulnerability by using specially-crafted Microsoft Office documents.\nAn attacker could craft a malicious ActiveX control to be used by a Microsoft Office document that hosts the browser rendering engine. The attacker would then have to convince the user to open the malicious document. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights.\nMicrosoft Defender Antivirus and Microsoft Defender for Endpoint both provide detection and protections for the known vulnerability. Customers should keep antimalware products up to date. Customers who utilize automatic updates do not need to take additional action. Enterprise customers who manage updates should select the detection build 1.349.22.0 or newer and deploy it across their environments. Microsoft Defender for Endpoint alerts will be displayed as: “Suspicious Cpl File Execution”.\nUpon completion of this investigation, Microsoft will take the appropriate action to help protect our customers. This may include providing a security update through our monthly release process or providing an out-of-cycle security update, depending on customer needs.\nPlease see the Mitigations and Workaround sections for important information about steps you can take to protect your system from this vulnerability.\nUPDATE September 14, 2021: Microsoft has released security updates to address this vulnerability. Please see the Security Updates table for the applicable update for your system. We recommend that you install these updates immediately. Please see the FAQ for important information about which updates are applicable to your system."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 8.8,
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:H/A:L/E:P/RL:O/RC:C",
"version": "3.1"
},
"format": "CVSS",
"scenarios": [
{
"lang": "en-US",
"value": "GENERAL"
}
]
}
],
"problemTypes": [
{
"descriptions": [
{
"description": "Remote Code Execution",
"lang": "en-US",
"type": "Impact"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-10T15:10:57.757Z",
"orgId": "f38d906d-7342-40ea-92c1-6c4a2c6478c8",
"shortName": "microsoft"
},
"references": [
{
"name": "Microsoft MSHTML Remote Code Execution Vulnerability",
"tags": [
"vendor-advisory",
"patch"
],
"url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-40444"
}
],
"title": "Microsoft MSHTML Remote Code Execution Vulnerability"
}
},
"cveMetadata": {
"assignerOrgId": "f38d906d-7342-40ea-92c1-6c4a2c6478c8",
"assignerShortName": "microsoft",
"cveId": "CVE-2021-40444",
"datePublished": "2021-09-15T11:24:26.000Z",
"dateReserved": "2021-09-02T00:00:00.000Z",
"dateUpdated": "2026-08-10T15:10:57.757Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}04 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-04",
"epss": 0.9784,
"percentile": 0.99907
}03 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-03",
"epss": 0.9784,
"percentile": 0.99907
}03 Nov 2026, 02:22 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-02",
"epss": 0.9784,
"percentile": 0.99907
}03 Nov 2026, 02:22 Jerusalem · CISA KEV status changed
Stored KEV snapshot at this observation.
{
"cveID": "CVE-2021-40444",
"cwes": [
"CWE-22"
],
"dateAdded": "2021-11-03",
"dueDate": "2021-11-17",
"forensicTriage": "No",
"knownRansomwareCampaignUse": "Known",
"notes": "https://nvd.nist.gov/vuln/detail/CVE-2021-40444",
"product": "MSHTML",
"requiredAction": "Apply updates per vendor instructions.",
"shortDescription": "Microsoft MSHTML contains a unspecified vulnerability that allows for remote code execution.",
"vendorProject": "Microsoft",
"vulnerabilityName": "Microsoft MSHTML Remote Code Execution Vulnerability"
}