Name:Windows Office Product Loaded MSHTML Module id:4cc015c9-687c-40d2-adcc-46350f66e10c version:2 date:2025-02-10 author:Michael Haag, Mauricio Velazco, Splunk status:production type:Anomaly Description:The following analytic detects the loading of the mshtml.dll module into an Office product, which is indicative of CVE-2021-40444 exploitation. It leverages Sysmon EventID 7 to monitor image loads by specific Office processes. This activity is significant because it can indicate an attempt to exploit a vulnerability in the MSHTML component via a malicious document. If confirmed malicious, this could allow an attacker to execute arbitrary code, potentially leading to system compromise, data exfiltration, or further network penetration. Data_source:
-Sysmon EventID 7
search:`sysmon` EventID=7 process_name IN ("EQNEDT32.exe", "excel.exe", "Graph.exe", "msaccess.exe", "mspub.exe", "onenote.exe", "onenoteim.exe", "onenotem.exe", "outlook.exe", "powerpnt.exe", "visio.exe", "winproj.exe", "winword.exe", "wordpad.exe", "wordview.exe") loaded_file_path IN ("*\\mshtml.dll", "*\\Microsoft.mshtml.dll","*\\IE.Interop.MSHTML.dll","*\\MshtmlDac.dll","*\\MshtmlDed.dll","*\\MshtmlDer.dll") | stats count min(_time) as firstTime max(_time) as lastTime by user_id, dest, process_name, loaded_file, loaded_file_path, original_file_name, process_guid | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `windows_office_product_loaded_mshtml_module_filter`
how_to_implement:To successfully implement this search, you need to be ingesting logs with the process names and image loads from your endpoints. If you are using Sysmon, you must have at least version 6.0.4 of the Sysmon TA. known_false_positives:Limited false positives will be present, however, tune as necessary. Some applications may legitimately load mshtml.dll. References: -https://app.any.run/tasks/36c14029-9df8-439c-bba0-45f2643b0c70/ -https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-40444 -https://strontic.github.io/xcyclopedia/index-dll -https://www.trustwave.com/en-us/resources/blogs/spiderlabs-blog/trojanized-onenote-document-leads-to-formbook-malware/ drilldown_searches: name:'View the detection results for - "$dest$"' search:'%original_detection_search% | search dest = "$dest$"' earliest_offset:'$info_min_time$' latest_offset:'$info_max_time$' name:'View risk events for the last 7 days for - "$dest$"' search:'| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$dest$") starthoursago=168 | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`' earliest_offset:'$info_min_time$' latest_offset:'$info_max_time$' tags: analytic_story: - 'Spearphishing Attachments' - 'Microsoft MSHTML Remote Code Execution CVE-2021-40444' - 'CVE-2023-36884 Office and Windows HTML RCE Vulnerability' asset_type:Endpoint cve: - 'CVE-2021-40444' mitre_attack_id: - 'T1566.001' product: - 'Splunk Enterprise' - 'Splunk Enterprise Security' - 'Splunk Cloud' security_domain:endpoint
