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CVE-2021-40444 - MSHTML RCE

This Playbook is part of the CVE-2021-40444 - MSHTML RCE Pack.#

Supported versions

Supported Cortex XSOAR versions: 5.5.0 and later.

CVE-2021-4044 refers to the MSHTML engine, that has been found vulnerable to arbitrary code execution by a specially crafted Microsoft Office document or rich text format file.


  • Microsoft official patch addressing CVE-2021-40444
  • Several workarounds suggested by Microsoft.

Researchers have validated this attack triggered in Windows Explorer with “Preview Mode” enabled, even in just a rich-text format RTF file (not an Office file and without ActiveX). This indicates it can be exploited even without opening the file and this invalidates Microsoft’s workaround mitigation mentioned above.

This playbook should be trigger manually and includes the following tasks:

  • Collect related known indicators from several sources.
  • Indicators, Files and Process creation patterns hunting using PAN-OS, Cortex XDR and SIEM products.
  • Block indicators automatically or manually.
  • Provide workarounds and detection capabilities.
  • Microsoft official CVE-2021-40444 patch.

More information: Microsoft MSHTML Remote Code Execution Vulnerability

Note: This is a beta playbook, which lets you implement and test pre-release software. Since the playbook is beta, it might contain bugs. Updates to the pack during the beta phase might include non-backward compatible features. We appreciate your feedback on the quality and usability of the pack to help us identify issues, fix them, and continually improve.


This playbook uses the following sub-playbooks, integrations, and scripts.


  • Block Indicators - Generic v2
  • Splunk Indicator Hunting
  • Palo Alto Networks - Hunting And Threat Detection
  • QRadar Indicator Hunting V2
  • Search Endpoints By Hash - Generic V2
  • Endpoint Enrichment - Generic v2.1


This playbook does not use any integrations.


  • ParseHTMLIndicators
  • http
  • SearchIncidentsV2


  • qradar-searches
  • associateIndicatorsToIncident
  • splunk-search
  • linkIncidents
  • closeInvestigation
  • extractIndicators
  • setIndicators

Playbook Inputs#

NameDescriptionDefault ValueRequired
YaraRulesSourceThe source of the Yara rules
SigmaRulesSourceThe source of the Sigma rules
SplunkEarliestTimeThe earliest time for the Splunk search query.-7dOptional
SplunkLatestTimeThe latest time for the Splunk search query.nowOptional
BlockIndicatorsAutomaticallyWhether to automatically block the indicators involved.FalseOptional
EDLDomainBlocklistThe name of the EDL Domain Block List.Demisto Remediation - Domain EDLOptional
QRadarTimeRangeThe time range for the QRadar search query.LAST 7 DAYSOptional

Playbook Outputs#

There are no outputs for this playbook.

Playbook Image#

CVE-2021-40444 - MSHTML RCE