CVE-2024-30102: Microsoft 365 Apps RCE Vulnerability

CVE-2024-30102 Overview

CVE-2024-30102 is a Use After Free (CWE-416) vulnerability in Microsoft Office that enables remote code execution. This memory corruption flaw exists in Microsoft 365 Apps and can be exploited by an attacker to execute arbitrary code in the context of the current user. The vulnerability requires local access and user interaction, but successful exploitation could lead to complete system compromise with high impact on confidentiality, integrity, and availability.

Critical Impact

Successful exploitation allows attackers to execute arbitrary code with the privileges of the current user, potentially leading to full system compromise, data theft, or lateral movement within enterprise environments.

Affected Products

• Microsoft 365 Apps for Enterprise (x64)
• Microsoft 365 Apps for Enterprise (x86)

Discovery Timeline

• June 11, 2024 - CVE-2024-30102 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2024-30102

Vulnerability Analysis

This vulnerability is classified as a Use After Free (CWE-416) memory corruption issue affecting Microsoft Office applications. Use After Free vulnerabilities occur when a program continues to use memory after it has been freed, leading to potential memory corruption. In this case, the flaw resides within Microsoft 365 Apps and can be triggered when processing specially crafted content.

The exploitation requires local access to the target system with low privileges, combined with user interaction such as opening a malicious document or clicking a link. Once triggered, the vulnerability allows an attacker to corrupt memory in a way that enables arbitrary code execution.

Root Cause

The vulnerability stems from improper memory management within Microsoft Office components. Specifically, the application fails to properly handle memory lifecycle, resulting in a condition where previously freed memory is subsequently accessed. This Use After Free condition can be manipulated by an attacker to achieve code execution by controlling the contents of the freed memory region before it is reused.

Attack Vector

The attack requires a local vector with user interaction. A threat actor could craft a malicious Office document that, when opened by a victim, triggers the Use After Free condition. The attacker must convince the user to open the malicious file through social engineering techniques such as phishing emails or compromised websites. Upon successful exploitation, the attacker gains code execution with the same privileges as the logged-in user.

The local attack vector means the malicious content must be delivered to the target system, typically through email attachments, file sharing services, or downloaded from malicious websites. The requirement for user interaction (opening the document) provides some protection, but social engineering attacks remain highly effective.

Detection Methods for CVE-2024-30102

Indicators of Compromise

• Unexpected crashes or abnormal behavior in Microsoft 365 Apps, particularly Word, Excel, or PowerPoint
• Unusual Office process spawning child processes or making network connections
• Memory corruption signatures in crash dumps from Office applications
• Suspicious Office documents with anomalous embedded content or macros

Detection Strategies

• Monitor for Office applications (WINWORD.EXE, EXCEL.EXE, POWERPNT.EXE) spawning unexpected child processes such as cmd.exe, powershell.exe, or wscript.exe
• Implement endpoint detection rules to identify memory corruption patterns in Office processes
• Deploy application whitelisting to prevent unauthorized code execution from Office contexts
• Enable Windows Defender Exploit Protection features including Data Execution Prevention (DEP) and Address Space Layout Randomization (ASLR)

Monitoring Recommendations

• Review Windows Event Logs for Office application crashes (Application Error events with Office process names)
• Monitor for suspicious file downloads in common document formats from untrusted sources
• Implement email gateway scanning for potentially malicious Office attachments
• Track Office application behavior using Sysmon or similar endpoint telemetry tools

How to Mitigate CVE-2024-30102

Immediate Actions Required

• Apply the latest Microsoft security updates for Microsoft 365 Apps immediately
• Restrict users from opening Office documents from untrusted sources
• Enable Protected View for files originating from the internet or email attachments
• Consider implementing Application Guard for Office to isolate potentially malicious documents

Patch Information

Microsoft has released a security update to address this vulnerability. Organizations should apply the patch available through the Microsoft Security Response Center advisory. The update can be deployed through Windows Update, Microsoft Update Catalog, or enterprise update management solutions such as Microsoft Endpoint Configuration Manager or Windows Server Update Services (WSUS).

Workarounds

• Enable Protected View in Office applications to open documents in a sandboxed read-only mode
• Configure Office to open documents from the internet in Application Guard containers
• Block Office file attachments from external email sources at the gateway level
• Implement strict macro policies to prevent automatic execution of embedded code
• Use file type blocking at the email gateway to filter high-risk Office document formats

# PowerShell: Enable Protected View settings via registry
Set-ItemProperty -Path "HKCU:\Software\Microsoft\Office\16.0\Word\Security\ProtectedView" -Name "DisableInternetFilesInPV" -Value 0 -Type DWord
Set-ItemProperty -Path "HKCU:\Software\Microsoft\Office\16.0\Word\Security\ProtectedView" -Name "DisableUnsafeLocationsInPV" -Value 0 -Type DWord
Set-ItemProperty -Path "HKCU:\Software\Microsoft\Office\16.0\Word\Security\ProtectedView" -Name "DisableAttachmentsInPV" -Value 0 -Type DWord