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Evidence dossier
CVE-2021-40444
Microsoft MSHTML Remote Code Execution Vulnerability
gen-56ccdaf9Normalized restatement
<p>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.</p> <p>An 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.</p> <p>Microsoft 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”.</p> <p>Upon 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.</p> <p>Please see the <strong>Mitigations</strong> and <strong>Workaround</strong> sections for important information about steps you can take to protect your system from this vulnerability.</p> <p><strong>UPDATE</strong> 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.</p>
- State
- PUBLISHED
- Published
- Sep 15, 2021
- Updated
- Mar 11, 2026
- Evidence coverage
- 72%
2026-07-18 · v2026.06.15 · percentile 99.9%
Distinct CVSS assessments remain side by side; none are averaged.
Source comparison
Who said what
Microsoft MSHTML Remote Code Execution Vulnerability
Microsoft MSHTML Remote Code Execution Vulnerability
Probability 0.968430000000; percentile 0.998820000000
Applicability
Cited product scope
[{"status": "affected", "version": "10.0.0", "lessThan": "10.0.10240.19060", "versionType": "custom"}]unknown[{"status": "affected", "version": "10.0.0", "lessThan": "10.0.14393.4651", "versionType": "custom"}]unknown[{"status": "affected", "version": "10.0.0", "lessThan": "10.0.17763.2183", "versionType": "custom"}]unknown[{"status": "affected", "version": "10.0.0", "lessThan": "10.0.18363.1801", "versionType": "custom"}]unknown[{"status": "affected", "version": "10.0.0", "lessThan": "10.0.19041.1237", "versionType": "custom"}]unknown[{"status": "affected", "version": "10.0.0", "lessThan": "10.0.19042.1237", "versionType": "custom"}]unknown[{"status": "affected", "version": "10.0.0", "lessThan": "10.0.19043.1237", "versionType": "custom"}]unknown[{"status": "affected", "version": "6.1.0", "lessThan": "6.1.7601.25712", "versionType": "custom"}, {"status": "affected", "version": "6.1.0", "lessThan": "1.001", "versionType": "custom"}, {"status": "affected", "version": "6.1.0", "lessThan": "6.1.7601.26221", "versionType": "custom"}]unknown[{"status": "affected", "version": "6.1.0", "lessThan": "6.1.7601.25712", "versionType": "custom"}, {"status": "affected", "version": "6.1.0", "lessThan": "1.001", "versionType": "custom"}, {"status": "affected", "version": "6.1.0", "lessThan": "6.1.7601.26221", "versionType": "custom"}]unknown[{"status": "affected", "version": "6.3.0", "lessThan": "6.3.9600.20120", "versionType": "custom"}, {"status": "affected", "version": "6.3.0", "lessThan": "1.001", "versionType": "custom"}]unknown[{"status": "affected", "version": "6.1.0", "lessThan": "6.1.7601.25712", "versionType": "custom"}, {"status": "affected", "version": "6.1.0", "lessThan": "1.001", "versionType": "custom"}]unknown[{"status": "affected", "version": "6.0.0", "lessThan": "6.1.7601.25712", "versionType": "custom"}, {"status": "affected", "version": "6.0.0", "lessThan": "1.001", "versionType": "custom"}]unknown[{"status": "affected", "version": "6.0.0", "lessThan": "6.0.6003.21218", "versionType": "custom"}, {"status": "affected", "version": "6.0.0", "lessThan": "1.001", "versionType": "custom"}]unknown[{"status": "affected", "version": "6.0.0", "lessThan": "6.0.6003.21218", "versionType": "custom"}, {"status": "affected", "version": "6.0.0", "lessThan": "1.001", "versionType": "custom"}]unknown[{"status": "affected", "version": "6.0.0", "lessThan": "6.0.6003.21218", "versionType": "custom"}, {"status": "affected", "version": "6.0.0", "lessThan": "1.001", "versionType": "custom"}]unknown[{"status": "affected", "version": "6.2.0", "lessThan": "6.2.9200.23462", "versionType": "custom"}, {"status": "affected", "version": "6.2.0", "lessThan": "1.001", "versionType": "custom"}]unknown[{"status": "affected", "version": "6.3.0", "lessThan": "6.3.9600.20120", "versionType": "custom"}, {"status": "affected", "version": "6.3.0", "lessThan": "1.001", "versionType": "custom"}]unknown[{"status": "affected", "version": "6.3.0", "lessThan": "6.3.9600.20120", "versionType": "custom"}, {"status": "affected", "version": "6.3.0", "lessThan": "1.001", "versionType": "custom"}]unknown[{"status": "affected", "version": "6.2.0", "lessThan": "6.2.9200.23462", "versionType": "custom"}, {"status": "affected", "version": "6.2.0", "lessThan": "1.001", "versionType": "custom"}]unknown[{"status": "affected", "version": "10.0.0", "lessThan": "10.0.14393.4651", "versionType": "custom"}]unknown[{"status": "affected", "version": "10.0.0", "lessThan": "10.0.14393.4651", "versionType": "custom"}]unknown[{"status": "affected", "version": "10.0.0", "lessThan": "10.0.17763.2183", "versionType": "custom"}]unknown[{"status": "affected", "version": "10.0.0", "lessThan": "10.0.17763.2183", "versionType": "custom"}]unknown[{"status": "affected", "version": "10.0.0", "lessThan": "10.0.20348.230", "versionType": "custom"}]unknown[{"status": "affected", "version": "10.0.0", "lessThan": "10.0.19041.1237", "versionType": "custom"}]unknown[{"status": "affected", "version": "10.0.0", "lessThan": "10.0.19042.1237", "versionType": "custom"}]unknowncpe:2.3:o:microsoft:windows_10_1507:*:*:*:*:*:*:*:*; end excluding 10.0.10240.19060supportedcpe:2.3:o:microsoft:windows_10_1607:*:*:*:*:*:*:*:*; end excluding 10.0.14393.4651supportedcpe:2.3:o:microsoft:windows_10_1809:*:*:*:*:*:*:*:*; end excluding 10.0.17763.2183supportedcpe:2.3:o:microsoft:windows_10_1909:*:*:*:*:*:*:*:*; end excluding 10.0.18363.1801supportedcpe:2.3:o:microsoft:windows_10_2004:*:*:*:*:*:*:*:*; end excluding 10.0.19041.1237supportedcpe:2.3:o:microsoft:windows_10_20h2:*:*:*:*:*:*:*:*; end excluding 10.0.19042.1237supportedcpe:2.3:o:microsoft:windows_10_21h1:*:*:*:*:*:*:*:*; end excluding 10.0.19043.1237supportedcpe:2.3:o:microsoft:windows_7:-:sp1:*:*:*:*:*:*supportedcpe:2.3:o:microsoft:windows_8.1:-:*:*:*:*:*:*:*supportedcpe:2.3:o:microsoft:windows_rt_8.1:-:*:*:*:*:*:*:*supportedcpe:2.3:o:microsoft:windows_server_2004:*:*:*:*:*:*:*:*; end excluding 10.0.19041.1237supportedcpe:2.3:o:microsoft:windows_server_2008:r2:sp1:*:*:*:*:x64:*supportedcpe:2.3:o:microsoft:windows_server_2008:-:sp2:*:*:*:*:*:*supportedcpe:2.3:o:microsoft:windows_server_2012:-:*:*:*:*:*:*:*supportedcpe:2.3:o:microsoft:windows_server_2012:-:r2:*:*:*:*:*:*supportedcpe:2.3:o:microsoft:windows_server_2016:*:*:*:*:*:*:*:*; end excluding 10.0.14393.4651supportedcpe:2.3:o:microsoft:windows_server_2019:*:*:*:*:*:*:*:*; end excluding 10.0.17763.2183supportedcpe:2.3:o:microsoft:windows_server_2022:*:*:*:*:*:*:*:*; end excluding 10.0.20348.230supportedcpe:2.3:o:microsoft:windows_server_20h2:*:*:*:*:*:*:*:*; end excluding 10.0.19042.1237supportedAssessments
CVSS by origin
AV:N/AC:M/Au:N/C:P/I:P/A:PCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:HCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:H/A:LCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:H/A:L/E:P/RL:O/RC:CLimitations and unknowns
- KEV membership is authoritative for the catalog, not proof of exposure in any environment.
- EPSS is a dated model probability and not an individual-environment prediction.
- Affected or fixed status applies only to the exact cited product and version scope; unresolved scope remains unknown.
- NVD-carried upstream facts remain derivative and are not independent corroboration.
- Only NVD metrics validated under the generation-bound calculator are Public Priority eligible; direct CVE record metrics remain display-only.
- NVD CVSS source eligibility is closed: NVD-authored, exact record-source, or registered same-CVE container origin; unmapped sources remain display-only.
- Factor D is unknown in Public Core because no accepted canonical mapping-obligation ledger is present.
- Core replay supports the active and immediately prior generation; retrospective valid-at replay is deferred.