cbcvebase.
CVE-2021-40444
published 2021-09-15

CVE-2021-40444: Microsoft is investigating reports of a remote code execution vulnerability in MSHTML that affects Microsoft Windows. Microsoft is aware of targeted attacks…

PriorityP191high7.8CVSS 3.1
AVLACLPRNUIRSUCHIHAH
KEVITWEXPLOITRansomwareInitial access
CISA Known Exploited Vulnerabilitydue 2021-11-17
Exploited in the wild
EPSS
97.24%
99.9th percentile
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. 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. 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”. 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. Please see the Mitigations and Workaround sections for important information about steps you can take to protect your system from this vulnerability. UPDATE 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.

Affected

59 ranges· showing 25
VendorProductVersion rangeFixed in
microsoftwindows_10_1507< 10.0.10240.1906010.0.10240.19060
microsoftwindows_10_1607< 10.0.14393.465110.0.14393.4651
microsoftwindows_10_1809< 10.0.17763.218310.0.17763.2183
microsoftwindows_10_1909< 10.0.18363.180110.0.18363.1801
microsoftwindows_10_2004< 10.0.19041.123710.0.19041.1237
microsoftwindows_10_20h2< 10.0.19042.123710.0.19042.1237
microsoftwindows_10_21h1< 10.0.19043.123710.0.19043.1237
microsoftwindows_10_version_1507>= 10.0.0 < 10.0.10240.1906010.0.10240.19060
microsoftwindows_10_version_1607>= 10.0.0 < 10.0.14393.465110.0.14393.4651
microsoftwindows_10_version_1809>= 10.0.0 < 10.0.17763.218310.0.17763.2183
microsoftwindows_10_version_1909>= 10.0.0 < 10.0.18363.180110.0.18363.1801
microsoftwindows_10_version_2004>= 10.0.0 < 10.0.19041.123710.0.19041.1237
microsoftwindows_10_version_20h2>= 10.0.0 < 10.0.19042.123710.0.19042.1237
microsoftwindows_10_version_21h1>= 10.0.0 < 10.0.19043.123710.0.19043.1237
microsoftwindows_7>= 6.1.0 < 6.1.7601.257126.1.7601.25712
microsoftwindows_7>= 6.1.0 < 1.0011.001
microsoftwindows_7>= 6.1.0 < 6.1.7601.262216.1.7601.26221
microsoftwindows_7_service_pack_1>= 6.1.0 < 6.1.7601.257126.1.7601.25712
microsoftwindows_7_service_pack_1>= 6.1.0 < 1.0011.001
microsoftwindows_7_service_pack_1>= 6.1.0 < 6.1.7601.262216.1.7601.26221
microsoftwindows_8.1>= 6.3.0 < 6.3.9600.201206.3.9600.20120
microsoftwindows_8.1>= 6.3.0 < 1.0011.001
microsoftwindows_server_2004< 10.0.19041.123710.0.19041.1237
microsoftwindows_server_2008
microsoftwindows_server_2008_r2_service_pack_1>= 6.0.0 < 6.1.7601.257126.1.7601.25712

Detection & IOCsextracted from sources · hover to see the quote

filenamecomres.cab
filenameIEcache.inf
filename1.doc.inf
filenameRequest Details.docx
otherCLSID:edbc374c-5730-432a-b5b8-de94f0b57217
urlhxxp://0x6B[.]0254.0113.0244:8090/payload.cab
urlhxxp://107[.]172.75.164:8090/microsoftonline.html
urlhxxp://www.code-nana.com/pjje/?t8LP2P=Mf6ydddwV/QU6mZ4nnZxMBdzDcAr2xsvfTgD82WAzYYrxOcjLRrG5mXLygKxYmvGqlzJAQ==&kPq8=K4Nh-6
urlhxxp://www.rajuherbalandspicegarden.com/pjje/?t8LP2P=DltNRLklEPawWuNnsQXifEZmZKsLvkDXv3cKYhiC/0Bh3Q72JrrG/8woD25qq/vxSOxjNQ==&kPq8=K4Nh-6
urlhxxp://www.swaplenders.com/pjje/?t8LP2P=TQtLDRoafbQM4/pEtdovke1/MPx0w24gCyByZx68z3lV5KTK6L4nUj2UtH2v2BgU+KkBhg==&kPq8=K4Nh-6
urlhxxp://www.thechiropractor.vegas/pjje/?t8LP2P=rpNmzTsgN3WrlTJLsfA2BlL5A0hwTnOMjBBWuUAz4iRkWF3ty9m96ejMesY0+5JvVxns9g==&kPq8=K4Nh-6
port8090
pathword/_rels/document.xml.rels
  • Exploit delivers a DLL disguised with a non-DLL extension (e.g. .inf) inside a CAB archive; hunt for DLL files with .inf or other mismatched extensions dropped from Office processes
  • Exploit chain uses CPL file execution to load the dropped DLL; monitor for control panel (rundll32/control.exe) loading unexpected DLLs spawned from Office processes
  • FormBook campaign stages second PowerShell payload hosted on Discord CDN (cdn.discordapp.com/attachments/); alert on Office or PowerShell processes fetching content from Discord attachment URLs
  • Exploit JavaScript uses CLSID edbc374c-5730-432a-b5b8-de94f0b57217 to check/load the CAB-delivered ActiveX control; presence of this CLSID in Office-spawned browser engine activity is a strong indicator of CVE-2021-40444 exploitation
  • Kaspersky detects CVE-2021-40444 exploitation attempts with verdict HEUR:Exploit.MSOffice.CVE-2021-40444.a; use this signature name for cross-vendor threat hunting
  • FortiGuard IPS signature MS.Office.MSHTML.Remote.Code.Execution covers network-level detection of CVE-2021-40444 exploitation traffic
  • Sender address [email protected] was associated with the CVE-2021-40444 testing-phase phishing email delivering Request Details.docx; use as an email IOC
  • ·Microsoft Defender Antivirus detection build 1.349.22.0 or newer is required for CVE-2021-40444 coverage; earlier builds will not detect the known exploitation samples
  • ·FortiGuard AV definitions version 88.00961 (or 88.00798 for W64/Agent.ASO!tr) are required for the listed AV signatures to fire; older definition sets will not cover these samples
  • ·Disabling ActiveX controls in Internet Explorer via registry edits is an effective mitigation but must be performed carefully; incorrect registry edits can cause severe OS issues
  • ·FortiGuard CDR protection requires the 'Enable/disable stripping of linked objects in Microsoft Office documents' option to be explicitly enabled; it is not on by default

CVSS provenance

nvdv3.17.8HIGHCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
nvdv2.06.8MEDIUMAV:N/AC:M/Au:N/C:P/I:P/A:P
vulncheck8.8HIGH
cisa7.8HIGH
vendor_msrc8.8HIGH
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