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[Vulnerabilities](https://unit42.paloaltonetworks.com/category/vulnerabilities/ "Vulnerabilities") [Vulnerabilities](https://unit42.paloaltonetworks.com/category/vulnerabilities/) # CVE-2023-36884 - Microsoft Office and Windows HTML Remote Code Execution: Threat Brief (Updated) ![Clock Icon](https://unit42.paloaltonetworks.com/wp-content/themes/unit42-v6/dist/images/icons/icon-clock.svg) 4 min read Related Products [![Advanced Threat Prevention icon](https://unit42.paloaltonetworks.com/wp-content/uploads/2024/06/strata_RGB_logo_Icon_Color.png)Advanced Threat Prevention](https://unit42.paloaltonetworks.com/product-category/advanced-threat-prevention/ "Advanced Threat Prevention")[![Advanced WildFire icon](https://unit42.paloaltonetworks.com/wp-content/uploads/2024/06/strata_RGB_logo_Icon_Color.png)Advanced WildFire](https://unit42.paloaltonetworks.com/product-category/advanced-wildfire/ "Advanced WildFire")[![Cloud-Delivered Security Services 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style="display: inline-block; width: 0px; overflow: hidden; line-height: 0;" class="mce\_SELRES\_start"\>\</span\> ## Executive Summary With July's Patch Tuesday release, Microsoft disclosed a zero-day Office and Windows HTML Remote Code Execution Vulnerability, CVE-2023-36884, which it rated "important" severity. Microsoft has observed active in-the-wild exploitation of this vulnerability using specially crafted Microsoft Office documents. It should be noted that exploitation requires the user to open the malicious document. Unit 42 Threat Intelligence can confirm that this vulnerability has been utilized since at least July 3, 2023. Further analysis is being conducted; an update will be made to this Threat Brief as the analysis is completed. Microsoft has released a [patch for Microsoft Office](https://msrc.microsoft.com/update-guide/vulnerability/ADV230003) that stops the attack chain leading to execution of this vulnerability. For those unable to patch, they recommend blocking Office applications from creating child processes or setting FEATURE\_BLOCK\_CROSS\_PROTOCOL\_FILE\_NAVIGATION registry key to avoid exploitation. See the [Security Updates](https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2023-36884) page for more information. Palo Alto Networks customers receive protections from and mitigations for CVE-2023-36884 in the following ways: * Organizations can engage the [Unit 42 Incident Response](https://start.paloaltonetworks.com/contact-unit42.html) team for specific assistance with this threat and others. * Cortex XDR and XSIAM agents help protect against post-exploitation activities associated with exploitation of CVE-2023-36884 as well as use Local Analysis detections for RomCom binaries on Windows environments. * Cortex XDR blocks the publicly known exploit chain for CVE-2023-36884. * Advanced WildFire can help detect and prevent attacks involving highly evasive malware. * Next-Generation Firewall with Advanced Threat Prevention security subscriptions can help block associated payloads and attack. * Cloud-Delivered Security Services can categorize C2 domains associated with this activity as malicious. Unit 42 will continue to monitor the situation for updated information, release of proof-of-concept code and evidence of more widespread exploitation. This brief will be updated as more information on the vulnerability and mitigations becomes available. |-------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------| | **Vulnerabilities Discussed** | [CVE-2023-36884](https://unit42.paloaltonetworks.com/tag/cve-2023-36884), [RomCom RAT](https://unit42.paloaltonetworks.com/tag/romcom-rat/) | ## Details of the Vulnerability With July's Patch Tuesday release, Microsoft disclosed a zero-day Office and Windows HTML Remote Code Execution Vulnerability, CVE-2023-36884, which it rated "important" severity. Microsoft has observed active in-the-wild exploitation of this vulnerability using specially crafted Microsoft Office documents. It should be noted that all exploitation examples seen so far require the user to open a malicious document. After the user opens the malicious document, it downloads a file containing a script that initiates an iframe injection resulting in the download of a malicious payload. It is not currently clear whether the underlying vulnerability is reliant on office documents for delivery. It is possible the vulnerability could be exploited using other, yet to be seen, delivery mechanisms. For example, Microsoft's security advisory includes a mitigation that recommends adding wordpad.exe as one of nine applications under a registry key that would block urls using the file: protocol originating from untrusted zones, such as the Internet zone or Restricted Sites zone. ## Current Scope of the Attack Unit 42 Threat Intelligence can confirm that this vulnerability has been utilized since at least July 3, 2023. Early exploitation of this vulnerability includes the use of the [RomCom](https://unit42.paloaltonetworks.com/tag/romcom-rat/) malware, which was reported by Microsoft on July 11, 2023. RomCom, originally observed by Unit 42 in May 2022, is a low-volume malware family that was historically observed in various attacks throughout the past year, including ransomware attacks, as well as targeted espionage-related attacks. The malware acts as a Remote Access Trojan (RAT), and provides an attacker with various capabilities including, but not limited to, directory listings, filesystem modifications, uploading and downloading files, and execution of processes. ## Interim Guidance Microsoft recommends blocking Office applications from creating child processes or setting the FEATURE\_BLOCK\_CROSS\_PROTOCOL\_FILE\_NAVIGATION registry key to avoid exploitation. See the [Security Updates](https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2023-36884) page for more information. ## Conclusion Based on the amount of publicly available information and current research and analysis, Palo Alto Networks highly recommends applying the [patch for Microsoft Office](https://msrc.microsoft.com/update-guide/vulnerability/ADV230003) to protect your organization. Palo Alto Networks and Unit 42 will continue to monitor the situation for updated information, release of proof-of-concept code and evidence of more widespread exploitation. Palo Alto Networks customers are protected by our products and services, as listed below. We will update this threat brief as more relevant information becomes available. Palo Alto Networks has shared our findings, including file samples and indicators of compromise, with our fellow Cyber Threat Alliance (CTA) members. CTA members use this intelligence to rapidly deploy protections to their customers and to systematically disrupt malicious cyber actors. Learn more about the [Cyber Threat Alliance](https://www.cyberthreatalliance.org/). ## Palo Alto Networks Product Protections for CVE-2023-36884 Palo Alto Networks customers can leverage a variety of product protections and updates to identify and defend against this threat. ### Unit 42 Incident Response If you think you may have been compromised or have an urgent matter, get in touch with the [Unit 42 Incident Response team](https://start.paloaltonetworks.com/contact-unit42.html) or call: * North America Toll-Free: 866.486.4842 (866.4.UNIT42) * EMEA: +31.20.299.3130 * APAC: +65.6983.8730 * Japan: +81.50.1790.0200 ### **Advanced Wildfire** Advanced WildFire uses multiple techniques (Automated Unpacking, Dependency Emulation, Run-Time Memory Analysis, Machine Learning, Static Analysis, Dynamic Analysis, Heuristic Analysis, and others) to detect and protect against RomCom and other highly evasive malware and variants of such. ### **Next-Generation Firewalls and Prisma Access With Advanced Threat Prevention** [Next-Generation Firewall](https://docs.paloaltonetworks.com/ngfw) with the [Advanced Threat Prevention](https://docs.paloaltonetworks.com/advanced-threat-prevention/administration) security subscription can help block the associated payloads and attack via the following Threat Prevention signatures: [86775](https://threatvault.paloaltonetworks.com/?query=86775), [86776](https://threatvault.paloaltonetworks.com/?query=86776), [86777](https://threatvault.paloaltonetworks.com/?query=86777). ### **Cloud-Delivered Security Services for the Next-Generation Firewall** Command and control (C2) domains associated with this malicious activity are categorized as malicious by [Advanced URL Filtering](https://docs.paloaltonetworks.com/pan-os/10-1/pan-os-new-features/url-filtering-features/advanced-url-filtering) and [DNS Security](https://docs.paloaltonetworks.com/dns-security). ### Cortex XSOAR [Cortex XSOAR](https://docs-cortex.paloaltonetworks.com/p/XSOAR) has released a response pack and playbook for [CVE-2023-36884](https://xsoar.pan.dev/docs/reference/playbooks/cve-2023-36884---microsoft-office-and-windows-html-rce) to help automate and speed the mitigation process. This playbook automates the following tasks: * Indicators of compromise (IoC) downloads and hunting * Threat hunting queries related to behavior identified as part of exploitation patterns * Microsoft mitigation actions The playbook can be triggered manually or run as a job. ### Cortex XDR and XSIAM [Cortex XDR](https://docs-cortex.paloaltonetworks.com/p/XDR) and [XSIAM](https://docs-cortex.paloaltonetworks.com/p/XSIAM) agents help protect against post-exploitation activities described in this article using Behavioral Threat Protection, the multiple protection modules and detect suspicious activity using Cortex Analytics as well as using Local Analysis detections for RomCom binaries on Windows environments. Cortex XDR blocks the publicly known exploit chain for CVE-2023-36884. ## Indicators of Compromise * a61b2eafcf39715031357df6b01e85e0d1ea2e8ee1dfec241b114e18f7a1163f * e7cfeb023c3160a7366f209a16a6f6ea5a0bc9a3ddc16c6cba758114dfe6b539 * 3a3138c5add59d2172ad33bc6761f2f82ba344f3d03a2269c623f22c1a35df97 * 48142dc7fe28a5d8a849fff11cb8206912e8382314a2f05e72abad0978b27e90 * 07377209fe68a98e9bca310d9749daa4eb79558e9fc419cf0b02a9e37679038d * 5f40cb4852ec50ee24f3cd951a172c725d02012d17dd645b6ce22d324aa140ad * 1a7bb878c826fe0ca9a0677ed072ee9a57a228a09ee02b3c5bd00f54f354930f * 0501d09a219131657c54dba71faf2b9d793e466f2c7fdf6b0b3c50ec5b866b2a * 74\.50.94\[.\]156 * 94\.232.40\[.\]34 * 66\.23.226\[.\]102 * 104\.234.239\[.\]26 * 65\.21.27\[.\]250 * finformservice\[.\]com * altimata\[.\]org * penofach\[.\]com * bentaxworld\[.\]com * wexonlake\[.\]com * ukrainianworldcongress\[.\]info *Updated July 13, 2023, at 3:00 p.m. PT to add Advanced Wildfire protections information.* *Updated July 13, 2023, at 8:45 p.m. PT to note status of patch and detection guidance.* *Updated July 14, 2023, at 11:58 a.m. PT to add protections information for Next-Generation Firewall and Cloud-Delivered Security Services. Cortex XDR and XSIAM protections information was updated. Details, attack scope, interim guidance, and threat hunting queries were added. IoCs are now listed.* *Updated July 17, 2023, at 4:15 p.m. PT to add Cortex XSOAR information.* *Updated August 9, 2023, at 10:35 a.m. PT to include patch released by Microsoft.* *Updated August 10, 2023, at 10:25 a.m. PT to include additional Cortex XDR protections.* Back to top ### Tags * [CVE-2023-36884](https://unit42.paloaltonetworks.com/tag/cve-2023-36884/ "CVE-2023-36884") * [Microsoft Office](https://unit42.paloaltonetworks.com/tag/microsoft-office/ "Microsoft Office") * [Microsoft Windows](https://unit42.paloaltonetworks.com/tag/microsoft-windows/ "Microsoft Windows") * [Remote Code Execution](https://unit42.paloaltonetworks.com/tag/remote-code-execution/ "Remote Code Execution") * [ROMCOM RAT](https://unit42.paloaltonetworks.com/tag/romcom-rat/ "ROMCOM RAT") [Threat Research Center](https://unit42.paloaltonetworks.com "Threat Research") [Next: Diplomats Beware: Cloaked Ursa Phishing With a Twist](https://unit42.paloaltonetworks.com/cloaked-ursa-phishing/ "Diplomats Beware: Cloaked Ursa Phishing With a Twist") ### Table of Contents * ### Related Articles * [Threat Brief: Exploitation of PAN-OS Captive Portal Zero-Day for Unauthenticated Remote Code Execution](https://unit42.paloaltonetworks.com/captive-portal-zero-day/ "article - table of contents") * [VShell and SparkRAT Observed in Exploitation of BeyondTrust Critical Vulnerability (CVE-2026-1731)](https://unit42.paloaltonetworks.com/beyondtrust-cve-2026-1731/ "article - table of contents") * [Critical Vulnerabilities in Ivanti EPMM Exploited](https://unit42.paloaltonetworks.com/ivanti-cve-2026-1281-cve-2026-1340/ "article - table of contents") ## Related Vulnerabilities Resources ![Pictorial representation of a group of people interacting with a dynamic 3D holographic display of colorful, undulating data waves on a table.](https://unit42.paloaltonetworks.com/wp-content/uploads/2025/09/11_Myth-Busting_Overview_1920x900-786x368.jpg) [![category icon](https://unit42.paloaltonetworks.com/wp-content/uploads/2025/08/Insights-icon-white.svg)Insights](https://unit42.paloaltonetworks.com/category/insights/) August 4, 2026 [#### The Frontier AI Vulnerability Burst: Industrializing Autonomous Zero-Day Discovery in Open-Source Software](https://unit42.paloaltonetworks.com/frontier-ai-vulnerability-burst/) * [AI](https://unit42.paloaltonetworks.com/tag/ai/ "AI") * [Frontier AI](https://unit42.paloaltonetworks.com/tag/frontier-ai/ "Frontier AI") * [Vulnerability Exploitation](https://unit42.paloaltonetworks.com/tag/vulnerability-exploitation/ "Vulnerability Exploitation") [Read now ![Right arrow](https://unit42.paloaltonetworks.com/wp-content/themes/unit42-v6/dist/images/icons/icon-right-arrow-withtail.svg)](https://unit42.paloaltonetworks.com/frontier-ai-vulnerability-burst/ "The Frontier AI Vulnerability Burst: Industrializing Autonomous Zero-Day Discovery in Open-Source Software") ![Pictorial representation of AI-enabled autonomous cyberattacks. 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Digital illustration of a map of North America with interconnected glowing lines and dots symbolizing network connections across the continent.](https://unit42.paloaltonetworks.com/wp-content/uploads/2026/05/06_Vulnerabilities_1920x900-3-1-786x368.jpg) [![category icon](https://unit42.paloaltonetworks.com/wp-content/uploads/2024/07/top-threats.svg)High Profile Threats](https://unit42.paloaltonetworks.com/category/top-cyberthreats/) May 6, 2026 [#### Threat Brief: Exploitation of PAN-OS Captive Portal Zero-Day for Unauthenticated Remote Code Execution](https://unit42.paloaltonetworks.com/captive-portal-zero-day/) * [CVE-2026-0300](https://unit42.paloaltonetworks.com/tag/cve-2026-0300/ "CVE-2026-0300") * [EarthWorm](https://unit42.paloaltonetworks.com/tag/earthworm/ "EarthWorm") * [PAN-OS](https://unit42.paloaltonetworks.com/tag/pan-os/ "PAN-OS") [Read now ![Right arrow](https://unit42.paloaltonetworks.com/wp-content/themes/unit42-v6/dist/images/icons/icon-right-arrow-withtail.svg)](https://unit42.paloaltonetworks.com/captive-portal-zero-day/ "Threat Brief: Exploitation of PAN-OS Captive Portal Zero-Day for Unauthenticated Remote Code Execution") ![Pictorial representation of a severe Linux vulnerability. Close-up of a woman wearing glasses and focusing intently on a computer screen.](https://unit42.paloaltonetworks.com/wp-content/uploads/2026/05/05_Vulnerabilities_1920x900-2-1-786x368.jpg) [![category icon](https://unit42.paloaltonetworks.com/wp-content/uploads/2024/07/top-threats.svg)High Profile Threats](https://unit42.paloaltonetworks.com/category/top-cyberthreats/) May 5, 2026 [#### Copy Fail: What You Need to Know About the Most Severe Linux Threat in Years](https://unit42.paloaltonetworks.com/cve-2026-31431-copy-fail/) * [Containers](https://unit42.paloaltonetworks.com/tag/containers/ "Containers") * [CVE-2026-31431](https://unit42.paloaltonetworks.com/tag/cve-2026-31431/ "CVE-2026-31431") * [Kubernetes](https://unit42.paloaltonetworks.com/tag/kubernetes/ "Kubernetes") [Read now ![Right arrow](https://unit42.paloaltonetworks.com/wp-content/themes/unit42-v6/dist/images/icons/icon-right-arrow-withtail.svg)](https://unit42.paloaltonetworks.com/cve-2026-31431-copy-fail/ "Copy Fail: What You Need to Know About the Most Severe Linux Threat in Years") ![Pictorial representation of CVE-2023-33538. Abstract image of a glowing red Wi-Fi symbol on a circuit board, with intricate patterns and a futuristic appearance.](https://unit42.paloaltonetworks.com/wp-content/uploads/2026/04/04_Vulnerabilities_1920x900-786x368.jpg) [![category icon](https://unit42.paloaltonetworks.com/wp-content/uploads/2024/06/icon-threat-research.svg)Threat Research](https://unit42.paloaltonetworks.com/category/threat-research/) April 16, 2026 [#### A Deep Dive Into Attempted Exploitation of CVE-2023-33538](https://unit42.paloaltonetworks.com/exploitation-of-cve-2023-33538/) * [Botnet](https://unit42.paloaltonetworks.com/tag/botnet/ "botnet") * [Command injection](https://unit42.paloaltonetworks.com/tag/command-injection/ "Command injection") * [CVE-2023-33538](https://unit42.paloaltonetworks.com/tag/cve-2023-33538/ "CVE-2023-33538") [Read now ![Right arrow](https://unit42.paloaltonetworks.com/wp-content/themes/unit42-v6/dist/images/icons/icon-right-arrow-withtail.svg)](https://unit42.paloaltonetworks.com/exploitation-of-cve-2023-33538/ "A Deep Dive Into Attempted Exploitation of CVE-2023-33538") ![Pictorial representation of BeyondTrust vulnerability CVE-2026-1731. Digital art depicting a stylized mountain range with vibrant blue and red hues. The peaks are accentuated by glowing particles and an abstract, starry backdrop, creating a futuristic landscape.](https://unit42.paloaltonetworks.com/wp-content/uploads/2026/02/14_Overview_1920x900-786x368.jpg) [![category icon](https://unit42.paloaltonetworks.com/wp-content/uploads/2024/07/top-threats.svg)High Profile Threats](https://unit42.paloaltonetworks.com/category/top-cyberthreats/) February 19, 2026 [#### VShell and SparkRAT Observed in Exploitation of BeyondTrust Critical Vulnerability (CVE-2026-1731)](https://unit42.paloaltonetworks.com/beyondtrust-cve-2026-1731/) * [Bash](https://unit42.paloaltonetworks.com/tag/bash/ "bash") * [CVE-2026-1731](https://unit42.paloaltonetworks.com/tag/cve-2026-1731/ "CVE-2026-1731") * [PowerShell](https://unit42.paloaltonetworks.com/tag/powershell/ "PowerShell") [Read now ![Right arrow](https://unit42.paloaltonetworks.com/wp-content/themes/unit42-v6/dist/images/icons/icon-right-arrow-withtail.svg)](https://unit42.paloaltonetworks.com/beyondtrust-cve-2026-1731/ "VShell and SparkRAT Observed in Exploitation of BeyondTrust Critical Vulnerability (CVE-2026-1731)") ![](https://unit42.paloaltonetworks.com/wp-content/uploads/2026/02/AdobeStock_1020436911-786x440.jpeg) [![category icon](https://unit42.paloaltonetworks.com/wp-content/uploads/2024/07/top-threats.svg)High Profile Threats](https://unit42.paloaltonetworks.com/category/top-cyberthreats/) February 17, 2026 [#### Critical Vulnerabilities in Ivanti EPMM Exploited](https://unit42.paloaltonetworks.com/ivanti-cve-2026-1281-cve-2026-1340/) * [CVE-2026-1281](https://unit42.paloaltonetworks.com/tag/cve-2026-1281/ "CVE-2026-1281") * [CVE-2026-1340](https://unit42.paloaltonetworks.com/tag/cve-2026-1340/ "CVE-2026-1340") * [Ivanti](https://unit42.paloaltonetworks.com/tag/ivanti/ "Ivanti") [Read now ![Right arrow](https://unit42.paloaltonetworks.com/wp-content/themes/unit42-v6/dist/images/icons/icon-right-arrow-withtail.svg)](https://unit42.paloaltonetworks.com/ivanti-cve-2026-1281-cve-2026-1340/ "Critical Vulnerabilities in Ivanti EPMM Exploited") ![Pictorial representation of CVE-2025-0921. Digital illustration of a map of North America with interconnected glowing lines and dots symbolizing network connections across the continent.](https://unit42.paloaltonetworks.com/wp-content/uploads/2026/01/06_Vulnerabilities_1920x900-2-1-786x368.jpg) [![category icon](https://unit42.paloaltonetworks.com/wp-content/uploads/2024/06/icon-threat-research.svg)Threat Research](https://unit42.paloaltonetworks.com/category/threat-research/) January 30, 2026 [#### Privileged File System Vulnerability Present in a SCADA System](https://unit42.paloaltonetworks.com/iconics-suite-cve-2025-0921/) * [CVE-2025-0921](https://unit42.paloaltonetworks.com/tag/cve-2025-0921/ "CVE-2025-0921") * [Privilege escalation](https://unit42.paloaltonetworks.com/tag/privilege-escalation/ "privilege escalation") * [SCADA](https://unit42.paloaltonetworks.com/tag/scada/ "SCADA") [Read now ![Right arrow](https://unit42.paloaltonetworks.com/wp-content/themes/unit42-v6/dist/images/icons/icon-right-arrow-withtail.svg)](https://unit42.paloaltonetworks.com/iconics-suite-cve-2025-0921/ "Privileged File System Vulnerability Present in a SCADA System") * ![Slider arrow](https://unit42.paloaltonetworks.com/wp-content/themes/unit42-v6/dist/images/icons/slider-arrow-left.svg) * ![Slider arrow](https://unit42.paloaltonetworks.com/wp-content/themes/unit42-v6/dist/images/icons/slider-arrow-left.svg) ![Close button](https://unit42.paloaltonetworks.com/wp-content/themes/unit42-v6/dist/images/icons/close-modal.svg) ![Enlarged Image]() ![Newsletter](https://unit42.paloaltonetworks.com/wp-content/uploads/2026/03/unit42-footer-subscribe-desktop.png) ![UNIT 42 Small Logo](https://unit42.paloaltonetworks.com/wp-content/themes/unit42-v6/dist/images/palo-alto-logo-small.svg) Get updates from Unit 42 ## Peace of mind comes from staying ahead of threats. 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